Upgrade `simd-json` to 0.13 (#2580) #720

Job	Run time
Test (nightly)	3m 30s
Test (stable)	5m 38s
Build docs	59s
Examples	4m 6s
Test (macOS)	6m 36s
Test (beta)	7m 6s
Check minimal versions	41s
Test (Windows)	4m 46s
MSRV	0s
Test (native-tls)	2m 52s
Test (no default features)	1m 29s
Test (no cache)	4m 21s
Test (no gateway)	2m 51s
Test (unstable Discord API features)	1m 12s
Test (simd-json)	6m 36s
Test (chrono, chrono)	1m 32s
Test (builder without model, builder, true)	1m 2s
Test (unstable Discord API (no default features), unstable_discord_api, true)	1m 9s
	56m 26s

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