Bump flatten-maven-plugin from 1.3.0 to 1.4.0 (#525)

pom.xml

@@ -412,7 +412,7 @@
           <plugin>
             <groupId>org.codehaus.mojo</groupId>
             <artifactId>flatten-maven-plugin</artifactId>
-            <version>1.3.0</version>
+            <version>1.4.0</version>
             <configuration>
               <updatePomFile>true</updatePomFile>
               <flattenMode>resolveCiFriendliesOnly</flattenMode>