refactor(@angular/build): increase piscina `idleTimeout` to 4s. #1333

Job	Run time
list	24s
workflow (build-cli)	1m 49s
workflow (build-unit-tests)	2m 12s
workflow (modules-builder-tests)	1m 37s
workflow (devkit-core-tests-rerun)	1m 31s
workflow (devkit-core-tests)	1m 15s
	8m 48s

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