Update dependency org.apache.maven.plugins:maven-javadoc-plugin to v3.8.0

Author: renovate[bot]

pom.xml

@@ -10,7 +10,7 @@
     <exec.mainClass>de.uzl.lied.mtbimporter.MtbImporter</exec.mainClass>
     <maven-source-plugin.version>3.3.1</maven-source-plugin.version>
     <maven-surefire-plugin.version>3.2.5</maven-surefire-plugin.version>
-    <maven-javadoc-plugin.version>3.6.3</maven-javadoc-plugin.version>
+    <maven-javadoc-plugin.version>3.8.0</maven-javadoc-plugin.version>
     <maven-enforcer-plugin.version>3.4.1</maven-enforcer-plugin.version>
   </properties>
   <repositories>