feat: enable flag for report generation (googleapis#1991)

* feat: enable flag for report generation

* chore: remove clirr-maven-plugin override

Author: jinseopkim0

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

@@ -60,13 +60,6 @@
           <groupId>org.codehaus.mojo</groupId>
           <artifactId>flatten-maven-plugin</artifactId>
         </plugin>
-      <plugin>
-        <groupId>org.codehaus.mojo</groupId>
-        <artifactId>clirr-maven-plugin</artifactId>
-        <configuration>
-          <skip>true</skip> <!-- TODO(gapic_upgrade): remove after first release -->
-        </configuration>
-      </plugin>
     </plugins>
   </build>
-</project>
+</project>