Extractors doc: correct linked example section (#3349)

Author: janxyz

axum/src/docs/extract.md

@@ -269,9 +269,9 @@ If an extractor fails it will return a response with the error and your
 handler will not be called. To customize the error response you have two 
 options:
 
-1. Use `Result<T, T::Rejection>` as your extractor like shown in ["Optional
-   extractors"](#optional-extractors). This works well if you're only using
-   the extractor in a single handler.
+1. Use `Result<T, T::Rejection>` as your extractor like shown in
+   ["Handling extractor rejections"](#handling-extractor-rejections).
+   This works well if you're only using the extractor in a single handler.
 2. Create your own extractor that in its [`FromRequest`] implementation calls
    one of axum's built in extractors but returns a different response for
    rejections. See the [customize-extractor-error] example for more details.