Remove help commands from built-ins #1162

Job	Run time
Clippy	49s
Test (MSRV)	1m 15s
Build docs	1m 8s
Test (stable)	1m 9s
Rustfmt	12s
Test (beta)	1m 13s
Test (nightly)	1m 8s
Test (macOS)	1m 3s
Test (Windows)	3m 31s
Test (no features)	1m 7s
Test (all features - simdjson, cargo test --all-features --lib --tests --examples)	1m 10s
Test (native TLS, cargo test --all-features --features serenity/native_tls_backend --lib --tests ...	1m 13s
	14m 58s

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