Update sbt-scalajs, scalajs-compiler, ... to 1.20.1 (#1957) #2841

Job	Run time
conformance	4m 27s
build (2_13, test)	10m 29s
build (3, e2e)	4m 38s
build (3, test)	8m 7s
build (2_13, e2e)	4m 27s
build (2_12, e2e)	3m 45s
build (2_12, test)	13m 55s
build (3, scala3_compat_test)	9m 52s
build (2_12, examples_and_formatting)	3m 5s
build (2_13, scala3_compat_test)	6m 53s
ci-passed	2s
	1h 9m 40s

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