ci: bump actions/checkout from 4.1.7 to 4.2.0 #554

Job	Run time
Build documentation	15s
no_std build (stable)	33s
Build and check benchmarks	59s
no_std build (nightly)	35s
Linux/ARM - Release tests (i686-unknown-linux-gnu)	1m 16s
Tests w. sanitizers	1m 21s
Linux/ARM - Release tests (armv7-unknown-linux-gnueabihf)	1m 42s
Linux/ARM - Release tests (powerpc64-unknown-linux-gnu)	1m 33s
WebAssembly - Release build (wasm32-unknown-unknown)	13s
test (stable, ubuntu-latest)	3m 19s
test (stable, macos-latest)	3m 1s
test (stable, windows-latest)	6m 59s
test (beta, ubuntu-latest)	3m 19s
test (beta, macos-latest)	2m 44s
test (beta, windows-latest)	5m 54s
test (nightly, ubuntu-latest)	3m 0s
test (nightly, macos-latest)	2m 50s
test (nightly, windows-latest)	5m 50s
test (1.80.0, ubuntu-latest)	3m 25s
test (1.80.0, macos-latest)	2m 59s
test (1.80.0, windows-latest)	5m 50s
	57m 37s

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