Update sbt-scalafmt to 2.5.6 in 0.11.x #2927

Job	Run time
conformance	4m 6s
build (2_12, e2e)	2m 21s
build (2_12, mima)	1m 40s
build (2_13, test)	2m 17s
build (3, e2e)	2m 26s
build (3, mima)	13s
build (2_13, scala3_compat_test)	2m 34s
build (2_13, e2e)	2m 13s
build (2_12, examples_and_formatting)	2m 5s
build (3, test)	2m 21s
build (2_12, test)	1m 31s
build (2_13, mima)	1m 36s
build (3, scala3_compat_test)	26s
ci-passed	0s
	25m 49s

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