chore(volo-thrift): fix clippy warning needless_as_bytes

[yukiiiteru]

Motivation

https://rust-lang.github.io/rust-clippy/master/index.html#needless_as_bytes

error: needless call to `as_bytes()`
   --> volo-thrift/src/codec/default/ttheader.rs:389:37
    |
389 |                         dst.put_u16(TT_HEADER_BIZ_STATUS_KEY.as_bytes().len() as u16);
    |                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: `len()` can be called directly on strings: `TT_HEADER_BIZ_STATUS_KEY.len()`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_as_bytes
    = note: `-D clippy::needless-as-bytes` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::needless_as_bytes)]`

Solution

Remote .as_bytes()