Fix `clippy` lint `empty_docs` #2008

Job	Run time
build_examples	4m 10s
build_nightly	1m 47s
build_benchmarks	53s
Check	1m 7s
Verify that web-sys is compiled correctly	56s
Clippy	6m 40s
dist_linux_aarch64_gnu	2m 41s
dist_macos_aarch64	1m 11s
dist_linux_x86_64_musl	2m 22s
dist_windows	2m 30s
dist_macos_x86_64	1m 22s
doc_api	1m 5s
doc_book	5s
Build and test the deno example	49s
Rustfmt	14s
Run js-sys crate tests	2m 21s
Run native tests	1m 57s
Run wasm-bindgen crate tests with multithreading enabled	1m 31s
Test TypeScript output of wasm-bindgen	1m 26s
Run UI compile-fail tests	40s
Run wasm-bindgen crate tests (unix)	4m 23s
Run web-sys crate tests	5m 6s
Run wasm-bindgen-webidl crate tests	2m 6s
test_examples	1m 47s
deploy	31s
	49m 40s

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