clippy: empty_line_after_doc_comments

[brooksprumo]

Problem

New clippy lints when upgrading to rust 1.84.0.

warning: empty line after doc comment
   --> streamer/src/nonblocking/quic.rs:232:1
    |
232 | / /// reduced when it is dropped.
233 | |
    | |_^
234 |   struct ClientConnectionTracker {
    |   ------------------------------ the comment documents this struct
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#empty_line_after_doc_comments
    = note: `#[warn(clippy::empty_line_after_doc_comments)]` on by default
    = help: if the empty line is unintentional remove it

Summary of Changes

Resolve the lints by using the suggestions from clippy and checking the code.

Partially fixes #4380

[brooksprumo]

Clippy suggested to change this to use //! syntax to document the module itself, but it seemed these comments felt more appropriate for the define_code! list below. Let me know if //! would be preferred here.

[LucasSte]

Those comments refer to the entire file, so I put them right at the beginning.

[brooksprumo]

Done. Fixed in 9e19e1c.

[mergify]

automerge label removed due to a CI failure