Remove magic from autocomplete #1138

Job	Run time
Build docs	1m 23s
Rustfmt	15s
Clippy	49s
Test (MSRV)	1m 19s
Test (stable)	2m 6s
Test (beta)	2m 1s
Test (nightly)	1m 35s
Test (macOS)	1m 29s
Test (Windows)	3m 49s
Test (no features)	1m 10s
Test (all features - simdjson, cargo test --all-features --lib --tests --examples)	1m 17s
Test (native TLS, cargo test --all-features --features serenity/native_tls_backend --lib --tests ...	1m 17s
	18m 30s

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