Update pom.xml

bot incorrectly bumped function-maven-plugin version

Author: maemayve

invoker/conformance/pom.xml

@@ -53,7 +53,7 @@
         <plugin>
           <groupId>com.google.cloud.functions</groupId>
           <artifactId>function-maven-plugin</artifactId>
-          <version>1.4.0</version>
+          <version>0.11.1</version>
         </plugin>
       </plugins>
     </pluginManagement>