Rust

Bump version to 20.3.1 #4613

Job	Run time
fmt	8s
build-and-test (msrv)	13m 49s
build-and-test (latest)	12m 21s
rust-analyzer-compat	2m 56s
publish-dry-run (macos-latest, aarch64-apple-darwin, --feature-powerset) / publish-dry-run	30m 33s
publish-dry-run (macos-latest, x86_64-apple-darwin, --feature-powerset) / publish-dry-run	36m 1s
publish-dry-run (ubuntu-latest, aarch64-unknown-linux-gnu, --feature-powerset) / publish-dry-run	21m 23s
publish-dry-run (ubuntu-latest, x86_64-unknown-linux-gnu, --feature-powerset) / publish-dry-run	13m 47s
publish-dry-run (windows-latest-8-cores, x86_64-pc-windows-msvc, --features opt --ignore-unknown-... / publish-dry-run	10m 52s
publish-dry-run (windows-latest-8-cores, x86_64-pc-windows-msvc) / publish-dry-run	9m 4s
complete	1s
	2h 30m 55s

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