Gateway cleanup #5928

Job	Run time
Test (nightly)	1m 37s
Check minimal versions	27s
Test (stable)	2m 5s
Test (beta)	2m 27s
Build docs	40s
Test (Windows)	3m 42s
Examples	2m 44s
Test (native-tls)	1m 57s
Test (macOS)	1m 28s
Test (no default features)	52s
Test (no cache)	2m 0s
MSRV	0s
Test (no gateway)	1m 28s
Test (unstable Discord API features)	2m 14s
Test (zlib compression)	2m 1s
Test (zstd compression)	2m 3s
Test (zlib and zstd compression)	2m 1s
Test (chrono, chrono)	57s
Test (unstable API + typesize, default unstable typesize, true)	59s
Test (builder without model, builder, true)	36s
Test (unstable Discord API (no default features), unstable, true)	44s
	33m 2s

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