Simplify MSRV Wasm testing configuration in CI. #1721

Job	Run time
cargo check (aarch64-android)	22s
cargo check (msrv) (wasm32)	42s
cargo clippy (windows-latest)	2m 4s
cargo check (msrv) (windows-latest)	1m 55s
cargo clippy (macos-latest)	1m 6s
cargo clippy (wasm32)	1m 16s
cargo check (msrv) (macos-latest)	38s
cargo doc	1m 40s
cargo clippy (ubuntu-latest)	1m 30s
cargo check (msrv) (ubuntu-latest)	49s
formatting	21s
Prime LFS Cache	3s
typos	4s
cargo test (wasm32)	29s
cargo test (windows-latest)	2m 9s
cargo test (macos-latest)	1m 12s
cargo test (ubuntu-latest)	2m 39s
	18m 59s

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