Bump MSRV to 1.31 #1337

Job	Run time
Check #[cfg]s	13s
macOS (x86_64-apple-darwin)	2m 19s
Build Channels Windows (stable)	2m 58s
Docker Linux Tier1 (i686-unknown-linux-gnu)	3m 22s
Style check	16s
Docker Linux Tier1 (x86_64-unknown-linux-gnu)	3m 18s
Windows (x86_64-pc-windows-gnu, 64, x86_64)	4m 30s
Windows (x86_64-pc-windows-msvc)	3m 13s
Windows (i686-pc-windows-msvc)	2m 28s
Build Channels macOS (stable, macos-13)	35s
Build Channels macOS (beta, macos-13)	47s
Build Channels macOS (nightly, macos-13)	2m 23s
Docker Linux Tier2 (aarch64-linux-android)	1m 6s
Docker Linux Tier2 (aarch64-unknown-linux-gnu)	52s
Docker Linux Tier2 (aarch64-unknown-linux-musl)	1m 7s
Docker Linux Tier2 (arm-linux-androideabi)	1m 7s
Docker Linux Tier2 (arm-unknown-linux-gnueabihf)	1m 7s
Docker Linux Tier2 (arm-unknown-linux-musleabihf)	1m 7s
Docker Linux Tier2 (i686-linux-android)	1m 7s
Docker Linux Tier2 (i686-unknown-linux-musl)	1m 7s
Docker Linux Tier2 (powerpc-unknown-linux-gnu)	1m 6s
Docker Linux Tier2 (powerpc64-unknown-linux-gnu)	1m 6s
Docker Linux Tier2 (powerpc64le-unknown-linux-gnu)	1m 6s
Docker Linux Tier2 (s390x-unknown-linux-gnu)	1m 7s
Docker Linux Tier2 (riscv64gc-unknown-linux-gnu)	1s
Docker Linux Tier2 (wasm32-wasip1)	1s
Docker Linux Tier2 (wasm32-wasip2)	1s
Docker Linux Tier2 (sparc64-unknown-linux-gnu)	1s
Docker Linux Tier2 (wasm32-unknown-emscripten)	1s
Docker Linux Tier2 (x86_64-linux-android)	1s
Docker Linux Tier2 (x86_64-unknown-linux-musl)	1s
Build Channels Linux	0s
success	1s
	39m 35s

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