Bump org.apache.maven:maven-compat (#113)

Bumps [org.apache.maven:maven-compat](https://github.com/apache/maven) from 3.3.9 to 3.8.1.
- [Release notes](https://github.com/apache/maven/releases)
- [Commits](apache/maven@maven-3.3.9...maven-3.8.1)

---
updated-dependencies:
- dependency-name: org.apache.maven:maven-compat
  dependency-type: direct:production
...

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openjpa-tools/openjpa-maven-plugin/pom.xml

@@ -42,7 +42,7 @@
     <inceptionYear>2011</inceptionYear>
     <properties>
         <checkstyle.suppressions.location>${project.basedir}${file.separator}..${file.separator}..${file.separator}openjpa-project${file.separator}suppressions.xml</checkstyle.suppressions.location>
-        <min.maven.version>3.3.9</min.maven.version>
+        <min.maven.version>3.8.1</min.maven.version>
     </properties>
     <prerequisites>
         <maven>${min.maven.version}</maven>