Upgrade maven-javadoc-plugin 3.6.2 -> 3.6.3 (#904)

See:
- https://github.com/apache/maven-javadoc-plugin/releases/tag/maven-javadoc-plugin-3.6.3
- apache/maven-javadoc-plugin@maven-javadoc-plugin-3.6.2...maven-javadoc-plugin-3.6.3

pom.xml

@@ -1111,7 +1111,7 @@
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-javadoc-plugin</artifactId>
-                    <version>3.6.2</version>
+                    <version>3.6.3</version>
                     <configuration>
                         <additionalJOptions>
                             <additionalJOption>--add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED</additionalJOption>