build: update actions/checkout action to v6 #2548

Job	Run time
list	19s
workflow (build-unit-tests)	2m 18s
workflow (devkit-core-tests-rerun)	1m 20s
workflow (build-cli)	1m 49s
workflow (modules-builder-tests)	1m 56s
workflow (devkit-core-tests)	1m 16s
	8m 58s

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