Javadoc warnings in build

### Affected version

HEAD

### Bug description

```
[WARNING] Unresolvable link in javadoc tag with value #getOutputName() found in target/maven-plugin-plugin-sources/org.apache.maven.reporting/maven-reporting-impl/4.0.0/sources/org/apache/maven/reporting/AbstractMavenReport.java:92: Could not resolve javadoc reference JavadocReference [moduleName=Optional.empty, packageNameClassName=Optional.empty, member=Optional[getOutputName()], label=Optional.empty]
[WARNING] Could not get javadoc URL for reference SiteTool#DEFAULT_LOCALE at FullyQualifiedJavadocReference [moduleName=Optional.empty, packageName=Optional[org.apache.maven.doxia.tools], className=Optional[SiteTool], memberType=Optional[FIELD], member=Optional[DEFAULT_LOCALE], label=Optional.empty, isExternal=true] (fully qualified target/maven-plugin-plugin-sources/org.apache.maven.reporting/maven-reporting-impl/4.0.0/sources/org/apache/maven/reporting/AbstractMavenReport.java:149): Found no javadoc site for FullyQualifiedJavadocReference [moduleName=Optional.empty, packageName=Optional[org.apache.maven.doxia.tools], className=Optional[SiteTool], memberType=Optional[FIELD], member=Optional[DEFAULT_LOCALE], label=Optional.empty, isExternal=true]
[WARNING] Could not get javadoc URL for reference SiteTool#getSiteLocales(String) at FullyQualifiedJavadocReference [moduleName=Optional.empty, packageName=Optional[org.apache.maven.doxia.tools], className=Optional[SiteTool], memberType=Optional[METHOD], member=Optional[getSiteLocales(java.lang.String)], label=Optional.empty, isExternal=true] (fully qualified target/maven-plugin-plugin-sources/org.apache.maven.reporting/maven-reporting-impl/4.0.0/sources/org/apache/maven/reporting/AbstractMavenReport.java:149): Found no javadoc site for FullyQualifiedJavadocReference [moduleName=Optional.empty, packageName=Optional[org.apache.maven.doxia.tools], className=Optional[SiteTool], memberType=Optional[METHOD], member=Optional[getSiteLocales(java.lang.String)], label=Optional.empty, isExternal=true]
[WARNING] Unresolvable link in javadoc tag with value #getOutputName() found in target/maven-plugin-plugin-sources/org.apache.maven.reporting/maven-reporting-impl/4.0.0/sources/org/apache/maven/reporting/AbstractMavenReport.java:92: Could not resolve javadoc reference JavadocReference [moduleName=Optional.empty, packageNameClassName=Optional.empty, member=Optional[getOutputName()], label=Optional.empty]
```