fix: bump actions/checkout from 5 to 6 #177

Job	Run time
Scan for Secrets	47s
validate-commit-message	46s
Verify Lets Encrypt CA Functionality	19s
lint-tests	2m 7s
Terraform	49s
test-compile-check	1m 47s
Lint Workflows	46s
shellcheck	49s
	8m 10s

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