Update scalafmt-core to 3.7.15 #1937

Job	Run time
build (2_12, mima)	1m 42s
build (2_12, e2e)	6s
conformance	1m 57s
build (2_12, test)	2m 54s
build (2_13, mima)	2m 2s
build (2_13, e2e)	10s
build (2_13, test)	2m 54s
build (3, mima)	6s
build (3, e2e)	10s
build (3, test)	2m 27s
build (2_12, examples_and_formatting)	2m 37s
build (2_13, scala3_compat_test)	2m 51s
build (3, scala3_compat_test)	2m 34s
ci-passed	0s
	22m 30s

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