Update sbt-mdoc to 2.5.1 (#1608) #1954

Job	Run time
conformance	2m 47s
build (2_12, mima)	2m 21s
build (2_12, e2e)	5s
build (2_12, test)	12m 55s
build (2_13, mima)	2m 14s
build (2_13, e2e)	7s
build (2_13, test)	12m 24s
build (3, mima)	5s
build (3, e2e)	5s
build (3, test)	9m 50s
build (2_12, examples_and_formatting)	2m 59s
build (2_13, scala3_compat_test)	10m 44s
build (3, scala3_compat_test)	9m 9s
ci-passed	1s
	1h 5m 46s

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