dependabot maven(deps): bump maven-pmd-plugin from 3.20.0 to 3.21.0

Bumps maven-pmd-plugin from 3.20.0 to 3.21.0.

Commits

• 3d87ac3 [maven-release-plugin] prepare release maven-pmd-plugin-3.21.0
• 05514fb [MPMD-375] Replace *ReportGenerators with a new *ReportRenderers
• 931a292 Clean up dependencies
• 7fc029a Clean up
• 73478ae [MPMD-374] Remove deprecated and unused PmdCollectingRenderer
• 8c5875a [MPMD-373] System property java.version is overwritten in ITs as model property
• fbd8644 [MPMD-372] Upgrade plugins and components (in ITs)
• 8c57b90 Auto-link MPMD Jira
• 40fe444 [MNG-6829] Replace any StringUtils#isEmpty(String) and #isNotEmpty(String) (#...
• 690dcbe [MPMD-366] Update parent pom to 39 (#118)
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