dependency: bump maven-pmd-plugin in /sevntu-checks

Bumps [maven-pmd-plugin](https://github.com/apache/maven-pmd-plugin) from 3.19.0 to 3.20.0.
- [Release notes](https://github.com/apache/maven-pmd-plugin/releases)
- [Commits](apache/maven-pmd-plugin@maven-pmd-plugin-3.19.0...maven-pmd-plugin-3.20.0)

---
updated-dependencies:
- dependency-name: org.apache.maven.plugins:maven-pmd-plugin
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

sevntu-checks/pom.xml

@@ -26,7 +26,7 @@
     <antrun.plugin.version>3.1.0</antrun.plugin.version>
     <sevntu.maven.plugin>RELEASE</sevntu.maven.plugin>
     <maven.jacoco.plugin.version>0.8.7</maven.jacoco.plugin.version>
-    <maven.pmd.plugin.version>3.19.0</maven.pmd.plugin.version>
+    <maven.pmd.plugin.version>3.20.0</maven.pmd.plugin.version>
     <pmd.version>6.50.0</pmd.version>
     <java.version>11</java.version>
     <junit.version>5.8.0</junit.version>