Fix builtin breakage due to collector rework #1228

Job	Run time
Build docs	1m 27s
Rustfmt	9s
Test (MSRV)	16s
Clippy	50s
Test (stable)	1m 39s
Test (beta)	1m 43s
Test (nightly)	1m 29s
Test (macOS)	1m 21s
Test (Windows)	4m 24s
Test (no features)	1m 8s
Test (native TLS, cargo test --all-features --features serenity/native_tls_backend --lib --tests ...	1m 28s
	15m 54s

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