Upgrade maven-javadoc-plugin 3.7.0 -> 3.8.0 (#1259)

See:
- https://issues.apache.org/jira/issues/?jql=project%20%3D%20MJAVADOC%20AND%20fixVersion%20%3E%203.7.0%20AND%20fixVersion%20%3C%3D%203.8.0
- https://github.com/apache/maven-javadoc-plugin/releases/tag/maven-javadoc-plugin-3.8.0
- apache/maven-javadoc-plugin@maven-javadoc-plugin-3.7.0...maven-javadoc-plugin-3.8.0

pom.xml

@@ -1123,7 +1123,7 @@
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-javadoc-plugin</artifactId>
-                    <version>3.7.0</version>
+                    <version>3.8.0</version>
                     <configuration>
                         <additionalJOptions>
                             <additionalJOption>--add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED</additionalJOption>