Update pom.xml

Incorrectly bumped maven plugin

Author: maemayve

invoker/conformance/pom.xml

@@ -53,7 +53,7 @@
         <plugin>
           <groupId>com.google.cloud.functions</groupId>
           <artifactId>function-maven-plugin</artifactId>
-          <version>1.4.1-SNAPSHOT</version>
+          <version>0.11.1</version>
         </plugin>
       </plugins>
     </pluginManagement>