Update sbt-mdoc to 2.5.1 #1952

Job	Run time
conformance	1m 49s
build (2_12, mima)	1m 16s
build (2_12, e2e)	5s
build (2_12, test)	16m 3s
build (2_13, mima)	1m 46s
build (2_13, e2e)	6s
build (2_13, test)	15m 3s
build (3, mima)	8s
build (3, e2e)	4s
build (3, test)	10m 21s
build (2_12, examples_and_formatting)	4m 10s
build (2_13, scala3_compat_test)	8m 16s
build (3, scala3_compat_test)	13m 1s
ci-passed	1s
	1h 12m 9s

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