HADOOP-15122. Lock down version of doxia-module-markdown plugin. Contributed by Marton Elek.

(cherry picked from commit 4bb765ee2e9fa16bb18c70d8f62ab885d883f414)

pom.xml

@@ -187,7 +187,7 @@ xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xs
             <dependency>
               <groupId>org.apache.maven.doxia</groupId>
               <artifactId>doxia-module-markdown</artifactId>
-              <version>1.8-SNAPSHOT</version>
+              <version>1.8</version>
             </dependency>
           </dependencies>
         </plugin>