Update CI script `actions/checkout` to v4 #442

Job	Run time
linux_archs (i386)	1m 48s
linux_checks (Debug, Default, Valgrind)	1m 10s
linux_archs (arm32v7)	13m 4s
linux_checks (Debug, Default, Sanitizer)	1m 7s
linux_clang_latest	1m 33s
linux_archs (arm64v8)	14m 20s
linux_gcc_latest	1m 58s
linux_checks (Debug, ReduceBinary, Valgrind)	57s
linux_archs (ppc64le)	11m 12s
linux_checks (Debug, ReduceBinary, Sanitizer)	59s
linux_archs (s390x)	12m 16s
linux_gcc4	45s
linux_checks (Release, Default, Valgrind)	1m 47s
linux_gcc5_i386	1m 12s
linux_archs (riscv64)	11m 0s
linux_checks (Release, Default, Sanitizer)	1m 27s
linux_checks (Release, ReduceBinary, Valgrind)	1m 40s
linux_tinycc	17s
linux_opts (gcc, no_fp)	46s
linux_checks (Release, ReduceBinary, Sanitizer)	55s
macos_clang	33s
linux_opts (gcc, no_reader)	29s
linux_checks (MinSizeRel, Default, Valgrind)	1m 36s
windows_msvc	2m 7s
linux_checks (MinSizeRel, Default, Sanitizer)	1m 20s
linux_opts (gcc, no_writer)	41s
linux_checks (MinSizeRel, ReduceBinary, Valgrind)	1m 0s
linux_opts (gcc, no_utf8)	1m 10s
codecov	54s
linux_opts (clang, no_fp)	45s
linux_checks (MinSizeRel, ReduceBinary, Sanitizer)	1m 38s
linux_opts (clang, no_reader)	30s
linux_opts (clang, no_writer)	34s
fuzzing	5m 33s
linux_opts (clang, no_utf8)	47s
	1h 39m 50s

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