Update scale-codec.md (#2178)

An `Option(None)` doesn't have an encoded value.

Author: josepot

content/md/en/docs/reference/scale-codec.md

@@ -43,7 +43,7 @@ The following table shows how the Rust implementation of the Parity SCALE codec
 | Results [^2]                  | Results are commonly used enumerations which indicate whether certain operations were successful or unsuccessful.                                                                                                                                                                                                                                                                                                                                                                    | `Ok(42)`                                                                                                            | `0x002a`                             |
 |                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      | `Err(false)`                                                                                                        | `0x0100`                             |
 | Options                       | One or zero values of a particular type.                                                                                                                                                                                                                                                                                                                                                                                                                                             | `Some`                                                                                                              | `0x01` followed by the encoded value |
-|                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      | `None`                                                                                                              | `0x00` followed by the encoded value |
+|                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      | `None`                                                                                                              | `0x00` |
 | Vectors (lists, series, sets) | A collection of same-typed values is encoded, prefixed with a _compact_ encoding of the number of items, followed by each item's encoding concatenated in turn.                                                                                                                                                                                                                                                                                                                      | Vector of unsigned 16-bit integers: `[4, 8, 15, 16, 23, 42]`                                                        | `0x18040008000f00100017002a00`       |
 | Strings                       | Strings are Vectors of bytes (`Vec<u8>`) containing a valid UTF8 sequence.                                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                     |                                      |
 | Tuples                        | A fixed-size series of values, each with a possibly different but predetermined and fixed type. This is simply the concatenation of each encoded value.                                                                                                                                                                                                                                                                                                                              | Tuple of compact unsigned integer and boolean: `(3, false)`                                                         | `0x0c00`                             |