fix(kad): wake `Handler` after pushing into `pending_messages` #14770

Job	Run time
Check rustdoc intra-doc links	37s
clippy (nightly-2023-09-10)	23s
Compile on wasm32-unknown-unknown	16s
Compile with select features (mdns tcp dns tokio)	15s
Compile with select features (mdns tcp dns async-std)	16s
Compile on wasm32-unknown-emscripten	15s
IPFS Integration tests	26s
Compile on wasm32-wasi	19s
Compile with MSRV	22s
Compile on x86_64-apple-darwin	21s
Run all WASM tests	37s
Compile on x86_64-pc-windows-msvc	13s
cargo-deny	25s
Check for changes in proto files	13s
Ensure that `Cargo.lock` is up-to-date	2s
examples	1s
gather_published_crates	1s
manifest_lint	1s
rustfmt	1s
semver	1s
Test ${{ matrix.crate }}	1s
	5m 6s

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