Update sbt-pgp to 2.3.1 #2348

Job	Run time
conformance	2m 20s
build (2_12, e2e)	3m 42s
build (2_12, test)	13m 8s
build (2_13, e2e)	4m 22s
build (2_13, test)	10m 30s
build (3, e2e)	4m 33s
build (3, test)	8m 59s
build (2_12, examples_and_formatting)	3m 18s
build (2_13, scala3_compat_test)	7m 26s
build (3, scala3_compat_test)	10m 38s
ci-passed	1s
	1h 8m 57s

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