Add `merge_group` trigger to required checks to prepare for merge queue #7047

Job	Run time
Ruby analysis (macos-latest, nightly-latest)	1m 21s
Ruby analysis (ubuntu-latest, nightly-latest)	53s
Ruby analysis (ubuntu-latest, default)	52s
Ruby analysis (macos-latest, default)	1m 5s
Ruby analysis (ubuntu-latest, linked)	46s
Ruby analysis (macos-latest, linked)	1m 4s
	6m 1s

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