Update coursier to 2.1.20 #2344

Job	Run time
conformance	1m 47s
build (2_12, e2e)	3m 48s
build (2_12, test)	11m 18s
build (2_13, e2e)	4m 5s
build (2_13, test)	11m 27s
build (3, e2e)	4m 35s
build (3, test)	9m 35s
build (2_12, examples_and_formatting)	2m 49s
build (2_13, scala3_compat_test)	7m 0s
build (3, scala3_compat_test)	8m 57s
ci-passed	1s
	1h 5m 22s

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