=sbt Update Scala 3 version to 3.1.3

[He-Pin]

https://github.com/lampepfl/dotty/releases/tag/3.1.3-RC3
More aggressive reduction of type selection (fixes parboiled2) scala/scala3#14987
Relax avoidance checks more for match type reduction scala/scala3#15036

[raboof]

Even though our Scala 3 support is still experimental, I don't think we should use -RC versions if we can help it, since I think you can use libraries compiled with 3.1.2 in a project using 3.1.3-RC3, but possibly not vice-versa (?).

[jrudolph]

Even though our Scala 3 support is still experimental, I don't think we should use -RC versions if we can help it, since I think you can use libraries compiled with 3.1.2 in a project using 3.1.3-RC3, but possibly not vice-versa (?).

Yep, good point, let's keep here until the final. Still good to have this PR testing against the latest version, as the previous versions of 3.1.3-RCs had the regression that broke everything...