chore: remove clirr-maven-plugin override

Author: jinseopkim0

grpc-google-cloud-datastore-v1/pom.xml

@@ -60,10 +60,6 @@
           <groupId>org.codehaus.mojo</groupId>
           <artifactId>flatten-maven-plugin</artifactId>
         </plugin>
-      <plugin>
-        <groupId>org.codehaus.mojo</groupId>
-        <artifactId>clirr-maven-plugin</artifactId>
-      </plugin>
     </plugins>
   </build>
 </project>