clientv3/integration: do not run fragmentation tests with gRPC Proxy

Signed-off-by: Gyuho Lee <gyuhox@gmail.com>

clientv3/integration/watch_fragment_test.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build !cluster_proxy
+
 package integration
 
 import (