Bump org.codehaus.mojo:flatten-maven-plugin from 1.5.0 to 1.6.0

Bumps [org.codehaus.mojo:flatten-maven-plugin](https://github.com/mojohaus/flatten-maven-plugin) from 1.5.0 to 1.6.0.
- [Release notes](https://github.com/mojohaus/flatten-maven-plugin/releases)
- [Commits](mojohaus/flatten-maven-plugin@1.5.0...1.6.0)

---
updated-dependencies:
- dependency-name: org.codehaus.mojo:flatten-maven-plugin
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

pom.xml

@@ -51,7 +51,7 @@
     <properties>
         <project.build.targetJdk>8</project.build.targetJdk>
         <!-- dependencies -->
-        <flatten-maven-plugin.version>1.5.0</flatten-maven-plugin.version>
+        <flatten-maven-plugin.version>1.6.0</flatten-maven-plugin.version>
         <!-- keep until SpotBugs #2732 is released, > 4.8.2 -->
         <dep.spotbugs.version>4.7.3</dep.spotbugs.version>
     </properties>