refactor(@angular-devkit/build-angular): remove redundant isFirstRun … #2803

Job	Run time
list	23s
workflow (modules-builder-tests)	1m 55s
workflow (devkit-core-tests)	1m 16s
workflow (devkit-core-tests-rerun)	1m 31s
workflow (build-unit-tests)	2m 28s
workflow (build-cli)	1m 34s
	9m 7s

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