Remove help commands from built-ins #1163

Job	Run time
Clippy	50s
Rustfmt	18s
Build docs	1m 23s
Test (MSRV)	1m 23s
Test (stable)	1m 54s
Test (beta)	2m 12s
Test (nightly)	1m 47s
Test (macOS)	1m 23s
Test (Windows)	5m 4s
Test (no features)	1m 11s
Test (all features - simdjson, cargo test --all-features --lib --tests --examples)	1m 18s
Test (native TLS, cargo test --all-features --features serenity/native_tls_backend --lib --tests ...	1m 18s
	20m 1s

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