Upgrade mockito to remove warning about illegal reflective access

git-svn-id: https://svn.apache.org/repos/asf/maven/plugins/trunk@1816954 13f79535-47bb-0310-9956-ffa450edef68

Author: rfscholte

maven-javadoc-plugin/pom.xml

@@ -287,7 +287,7 @@ under the License.
     <dependency>
       <groupId>org.mockito</groupId>
       <artifactId>mockito-core</artifactId>
-      <version>1.8.5</version>
+      <version>2.12.0</version>
       <scope>test</scope>
     </dependency>
     <dependency>