Update actions/checkout to v4 (#1886) #1924

Job	Run time
License Header and Formatting Checks	6m 53s
Integration Tests on swiftlang/swift:nightly-jammy	4m 24s
Build and Test on swiftlang/swift:nightly-jammy	5m 37s
Performance Tests on swiftlang/swift:nightly-jammy	3m 28s
Integration Tests on swift:5.10-jammy	3m 10s
Build and Test on swift:5.10-jammy	4m 4s
Performance Tests on swift:5.10-jammy	2m 55s
Build and Test on swift:5.9-jammy	4m 2s
Performance Tests on swift:5.9-jammy	2m 54s
Build and Test on swift:5.8-focal	3m 44s
Integration Tests on swift:5.9-jammy	3m 14s
Performance Tests on swift:5.8-focal	2m 23s
Integration Tests on swift:5.8-focal	2m 49s
	49m 37s

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