Update coursier to 2.1.15 #2305

Job	Run time
conformance	1m 56s
build (2_12, e2e)	3m 32s
build (2_12, test)	10m 14s
build (2_13, e2e)	4m 8s
build (2_13, test)	10m 22s
build (3, e2e)	4m 24s
build (3, test)	9m 18s
build (2_12, examples_and_formatting)	2m 49s
build (2_13, scala3_compat_test)	8m 55s
build (3, scala3_compat_test)	10m 0s
ci-passed	1s
	1h 5m 39s

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