Fix maven-enforcer-plugin version.

Author: heuermh

pom.xml

@@ -237,7 +237,7 @@
         <plugins>
           <plugin>
             <artifactId>maven-enforcer-plugin</artifactId>
-            <version>3.0.0-M5</version>
+            <version>3.0.0-M3</version>
           </plugin>
           <plugin>
             <artifactId>maven-gpg-plugin</artifactId>