Remove `disable_combine_sarif_files` feature flag #4116

Job	Run time
Resolve environment (ubuntu-latest, default)	43s
Resolve environment (windows-latest, nightly-latest)	3m 11s
Resolve environment (windows-latest, linked)	2m 43s
Resolve environment (ubuntu-latest, linked)	1m 5s
Resolve environment (windows-latest, default)	1m 2s
Resolve environment (ubuntu-latest, nightly-latest)	1m 0s
Resolve environment (macos-latest, nightly-latest)	2m 55s
Resolve environment (macos-latest, default)	2m 39s
Resolve environment (macos-latest, linked)	2m 25s
	17m 43s

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