ci: update cargo-check-external-types toolchain #1611

Job	Run time
Validate external types appearing in public API	53s
Clippy	36s
Measure coverage	51s
Check cross compilation targets	37s
Cargo Deny	8s
Feature Powerset	37s
MSRV	1m 9s
Verify that no-std modes do not rely on libstd (--no-default-features)	6s
Cargo Package	1m 5s
Check for documentation errors (stable)	30s
Verify that no-std modes do not rely on libstd (--no-default-features --features alloc)	12s
Check for documentation errors (beta)	37s
Format	8s
Check for documentation errors (nightly)	35s
Check semver compatibility	27s
Build+test (--all-features, stable)	49s
Build+test (stable, ubuntu-latest)	42s
Build+test (--features=alloc, stable, ubuntu-latest)	47s
Build+test (--no-default-features, stable, ubuntu-latest)	40s
Build+test (--no-default-features --features alloc,std, stable, ubuntu-latest)	33s
Build+test (--all-features, --release, stable, ubuntu-latest)	1m 22s
Build+test (--all-features, nightly, ubuntu-latest)	53s
Build+test (--all-features, beta, ubuntu-latest)	52s
Build+test (--no-default-features --features alloc,std,aws_lc_rs, stable, macos-latest)	51s
Build+test (--no-default-features --features alloc,std,aws_lc_rs, stable, windows-latest)	3m 29s
Build+test (--no-default-features --features alloc,std,aws_lc_rs, stable, ubuntu-latest)	52s
	20m 21s

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