Fix clippy lints #1048

Job	Run time
Test (nightly)	3m 4s
Test (macOS)	2m 0s
Test (stable)	2m 45s
Test (beta)	3m 3s
Build docs	1m 0s
Examples	4m 6s
Test (Windows)	6m 25s
Test (native-tls)	2m 39s
Check minimal versions	1m 7s
Test (no default features)	47s
MSRV	0s
Test (no cache)	2m 32s
Test (no gateway)	1m 39s
Test (unstable Discord API features)	2m 42s
Test (simd-json)	2m 38s
Test (chrono, chrono)	49s
Test (unstable API + typesize, default unstable_discord_api typesize, true)	58s
Test (builder without model, builder, true)	40s
Test (unstable Discord API (no default features), unstable_discord_api, true)	40s
	39m 34s

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