Update Dependabot configuration for GitHub Actions #5144

Job	Run time
Diagnostic export (ubuntu-latest, linked)	1m 9s
Diagnostic export (windows-latest, nightly-latest)	2m 46s
Diagnostic export (macos-latest, nightly-latest)	1m 6s
Diagnostic export (macos-latest, linked)	1m 9s
Diagnostic export (ubuntu-latest, nightly-latest)	1m 0s
Diagnostic export (windows-latest, linked)	2m 34s
	9m 44s

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