Bump org.codehaus.mojo:flatten-maven-plugin from 1.5.0 to 1.6.0 (#519)

pom.xml

@@ -869,7 +869,7 @@
           <plugin>
             <groupId>org.codehaus.mojo</groupId>
             <artifactId>flatten-maven-plugin</artifactId>
-            <version>1.5.0</version>
+            <version>1.6.0</version>
             <configuration>
               <updatePomFile>true</updatePomFile>
             </configuration>