UP-4370 ignore IntelliJ-generated overlays directories on license check.

[UP-4370](https://issues.jasig.org/browse/UP-4370) : widen the exclusion match in the licensing plugin configuration in `pom.xml` to ignore the IntelliJ-generated `overlays` directories when applying license check.

This issue tripped up the uPortal `4.2.0-M1` release process momentarily.