build

Remove `--nworkers` (#2759) #6374

Job	Run time
format-check	5m 26s
build-mdbook	8s
scaladoc-check	3m 55s
integration-tests (ubuntu-latest, oopsla19)	20m 19s
unit-tests (ubuntu-latest)	9m 53s
integration-tests (ubuntu-latest, arrays)	13m 31s
unit-tests (macos-latest)	12m 53s
integration-tests (macos-latest, oopsla19)	33m 32s
compiler-warnings	3m 23s
docker-tests	27m 43s
	2h 10m 43s

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