.github: Bump actions/checkout from 3 to 4 #52

Job	Run time
race-build	3m 28s
race-root-integration (1/4)	1m 8s
race-root-integration (2/4)	1m 10s
test (amd64, -coverprofile=/tmp/coverage.out)	13m 20s
race-root-integration (3/4)	1m 11s
test (amd64, -race, 1/3)	5m 3s
race-root-integration (4/4)	1m 9s
test (amd64, -race, 2/3)	13m 49s
test (amd64, -race, 3/3)	5m 15s
windows	6m 21s
test (386)	13m 17s
cross (linux, arm64)	3m 5s
cross (linux, 386)	3m 10s
vm	0s
cross (linux, loong64)	3m 7s
cross (linux, arm, 5)	3m 2s
cross (linux, arm, 7)	4m 10s
cross (darwin, amd64)	3m 4s
android	52s
cross (darwin, arm64)	3m 1s
depaware	28s
cross (windows, amd64)	2m 40s
fuzz	6m 44s
cross (windows, arm64)	2m 38s
go_generate	53s
cross (freebsd, amd64)	3m 3s
cross (openbsd, amd64)	2m 54s
go_mod_tidy	27s
ios	40s
cross (plan9, amd64)	18s
licenses	6s
staticcheck (linux, amd64)	2m 54s
tailscale_go	27s
staticcheck (windows, amd64)	2m 41s
wasm	7m 32s
staticcheck (darwin, amd64)	2m 50s
staticcheck (windows, 386)	2m 42s
notify_slack	9s
check_mergeability	1s
	2h 8m 49s

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