fix(@angular/cli): ignore unknown files when formatting schematic cha… #9876

Job	Run time
lint	52s
build-e2e-windows	52s
build	52s
e2e-windows	1s
publish-snapshots	1s
Browser Compatibility Tests	1s
e2e-package-managers	1s
test	1s
e2e-snapshots	1s
e2e	1s
	2m 43s

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