Add `cooldown` settings for Dependabot #2484

Job	Run time
Upload debug artifacts (default)	6m 29s
Upload debug artifacts (nightly-latest)	6m 39s
Upload debug artifacts (linked)	6m 40s
Upload debug artifacts (stable-v2.20.3)	6m 2s
Download and check debug artifacts	8s
	25m 58s

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