Simplify per-platform package exclusion in CI. #1621

Job	Run time
cargo test (windows-latest)	1m 47s
cargo clippy (windows-latest)	34s
cargo test (macos-latest)	27s
cargo check (msrv) (wasm32)	28s
cargo clippy (macos-latest)	35s
cargo test (ubuntu-latest)	49s
cargo check (msrv) (windows-latest)	1m 45s
cargo clippy (ubuntu-latest)	48s
cargo check (msrv) (macos-latest)	28s
cargo clippy (wasm32)	1m 1s
cargo check (msrv) (ubuntu-latest)	38s
compare snapshots (windows-latest)	1m 2s
compare snapshots (macos-latest)	30s
cargo doc (windows-latest)	1m 50s
formatting	42s
compare snapshots (ubuntu-latest)	32s
cargo test (wasm32)	1m 10s
cargo doc (macos-latest)	37s
cargo doc (ubuntu-latest)	1m 20s
typos	4s
	17m 7s

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