Update the node version in the GitHub workflows from 16 to 20 #1497

Job	Run time
Run wasm-bindgen crate tests (unix)	11m 28s
Check	2m 11s
Rustfmt	15s
Clippy	9m 31s
Build and test the deno example	1m 32s
Verify that web-sys is compiled correctly	1m 21s
Run js-sys crate tests	3m 23s
Run native tests	3m 31s
Run wasm-bindgen crate tests with multithreading enabled	4m 25s
Test TypeScript output of wasm-bindgen	1m 41s
Run web-sys crate tests	11m 20s
Run wasm-bindgen-webidl crate tests	3m 8s
build_benchmarks	1m 50s
build_examples	6m 22s
build_nightly	2m 24s
dist_linux_aarch64_gnu	5m 20s
dist_macos_aarch64	4m 7s
dist_macos_x86_64	2m 1s
dist_linux_x86_64_musl	4m 53s
dist_windows	5m 29s
doc_api	1m 47s
doc_book	25s
Run UI compile-fail tests	6m 5s
test_examples	4m 19s
deploy	1m 10s
	1h 39m 58s

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