add checkout action to detect-changes step #2827

Job	Run time
compliance-tests	5m 20s
build-and-test-minimal	57s
compliance-tests-detect-changes	3s
build-and-test	1m 53s
e2e-tests	1m 34s
build-and-test-msrv	1m 0s
check-bindings	1m 11s
format	5s
compliance-tests-og	0s
compliance-tests-lint	0s
clippy	19s
docs	11s
audit	7s
miri	51s
	13m 31s

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