Update coursier to 2.1.21 (#1785) #2353

Job	Run time
conformance	1m 38s
build (2_12, e2e)	3m 26s
build (2_12, test)	13m 5s
build (2_13, e2e)	4m 4s
build (2_13, test)	11m 1s
build (3, e2e)	4m 12s
build (3, test)	8m 19s
build (2_12, examples_and_formatting)	2m 35s
build (2_13, scala3_compat_test)	8m 2s
build (3, scala3_compat_test)	7m 6s
ci-passed	1s
	1h 3m 29s

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