codec: fix typo in the docs for Encoder::Error (#6800)

tokio-util/src/codec/encoder.rs

@@ -9,7 +9,7 @@ pub trait Encoder<Item> {
  /// The type of encoding errors.
  ///
  /// [`FramedWrite`] requires `Encoder`s errors to implement `From<io::Error>`
- /// in the interest letting it return `Error`s directly.
+ /// in the interest of letting it return `Error`s directly.
  ///
  /// [`FramedWrite`]: crate::codec::FramedWrite
  type Error: From<io::Error>;