Remove `*_arc` methods (#2654) #790

# to view logs

Job	Run time
Test (macOS)	6m 28s
Test (stable)	3m 10s
Build docs	36s
Examples	4m 21s
Test (beta)	2m 55s
Test (Windows)	5m 13s
Test (native-tls)	3m 26s
Check minimal versions	35s
MSRV	0s
Test (no default features)	40s
Test (nightly)	3m 7s
Test (no cache)	2m 55s
Test (no gateway)	1m 45s
Test (unstable Discord API features)	3m 5s
Test (simd-json)	3m 14s
Test (chrono, chrono)	39s
Test (unstable API + typesize, default unstable_discord_api typesize, true)	1m 1s
Test (builder without model, builder, true)	27s
Test (unstable Discord API (no default features), unstable_discord_api, true)	28s
	44m 5s

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