=tes #15777 simple, but stable fix to , or . sensitivity in spec

Solves #15777

Conflicts:
	akka-testkit/src/test/scala/akka/testkit/metrics/reporter/PrettyDurationSpec.scala
Merge pull request #15789 from ktoso/port-prettydurationspec-ktoso

=tes #15777 simple, but stable fix to , or . sensitivity in spec (for Validation)