HADOOP-14056. Update maven-javadoc-plugin to 2.10.4.

(cherry picked from commit fad766e1d255648ee5dd9bc1f58cef42b930bc83)

hadoop-project/pom.xml

@@ -1368,7 +1368,7 @@
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-javadoc-plugin</artifactId>
-          <version>2.8.1</version>
+          <version>${maven-javadoc-plugin.version}</version>
           <configuration>
             <additionalparam>-Xmaxwarns 10000</additionalparam>
           </configuration>

pom.xml

@@ -98,7 +98,7 @@ xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/x
     <maven-assembly-plugin.version>2.4</maven-assembly-plugin.version>
     <maven-dependency-plugin.version>2.8</maven-dependency-plugin.version>
     <maven-enforcer-plugin.version>1.4.1</maven-enforcer-plugin.version>
-    <maven-javadoc-plugin.version>2.9.1</maven-javadoc-plugin.version>
+    <maven-javadoc-plugin.version>2.10.4</maven-javadoc-plugin.version>
     <maven-gpg-plugin.version>1.5</maven-gpg-plugin.version>
     <apache-rat-plugin.version>0.10</apache-rat-plugin.version>
     <wagon-ssh.version>1.0</wagon-ssh.version>