Remove examples section from the root README (#558)

The example was copied verbatim from chacha20 and we do not check it in
CI. Users should arguably use specific crate doc examples instead.

Author: newpavlov

README.md

@@ -37,50 +37,6 @@ The following describes the security level ratings associated with each hash fun
 | :yellow_heart: | Theoretical break: security lower than claimed |
 | :broken_heart: | Attack demonstrated in practice: avoid if at all possible |
 
-## Example
-
-Crates functionality is expressed in terms of traits defined in the [`cipher`] crate.
-
-Let's use ChaCha20 to demonstrate usage of synchronous stream cipher:
-
-```rust
-use chacha20::ChaCha20;
-// Import relevant traits
-use chacha20::cipher::{KeyIvInit, StreamCipher, StreamCipherSeek};
-use hex_literal::hex;
-
-let key = [0x42; 32];
-let nonce = [0x24; 12];
-let plaintext = hex!("00010203 04050607 08090a0b 0c0d0e0f");
-let ciphertext = hex!("e405626e 4f1236b3 670ee428 332ea20e");
-
-// Key and IV must be references to the `GenericArray` type.
-// Here we use the `Into` trait to convert arrays into it.
-let mut cipher = ChaCha20::new(&key.into(), &nonce.into());
-
-let mut buffer = plaintext;
-
-// apply keystream (encrypt)
-cipher.apply_keystream(&mut buffer);
-assert_eq!(buffer, ciphertext);
-
-let ciphertext = buffer;
-
-// ChaCha ciphers support seeking
-cipher.seek(0u32);
-
-// decrypt ciphertext by applying keystream again
-cipher.apply_keystream(&mut buffer);
-assert_eq!(buffer, plaintext);
-
-// stream ciphers can be used with streaming messages
-cipher.seek(0u32);
-for chunk in buffer.chunks_mut(3) {
-    cipher.apply_keystream(chunk);
-}
-assert_eq!(buffer, ciphertext);
-```
-
 ## License
 
 All crates licensed under either of