Bump pmd.version from 6.14.0 to 6.15.0
Bump pmd.version from 6.14.0 to 6.15.0

Bumps `pmd.version` from 6.14.0 to 6.15.0.

Updates `pmd-core` from 6.14.0 to 6.15.0
- [Release notes](https://github.com/pmd/pmd/releases)
- [Commits](https://github.com/pmd/pmd/compare/pmd_releases/6.14.0...pmd_releases/6.15.0)

Updates `pmd-java` from 6.14.0 to 6.15.0
- [Release notes](https://github.com/pmd/pmd/releases)
- [Commits](https://github.com/pmd/pmd/compare/pmd_releases/6.14.0...pmd_releases/6.15.0)
jenkinsci/analysis-model,jenkinsci/analysis-model,jenkinsci/analysis-model,jenkinsci/analysis-model