SingleUserGroupTest: Remove unnecessary groupBackend member

The GroupBackend is provided in the base class.

Change-Id: I61500178ca37af70e002f4d46fcdc534f8cde325

src/test/java/com/googlesource/gerrit/plugins/singleusergroup/SingleUserGroupTest.java

diff --git a/src/test/java/com/googlesource/gerrit/plugins/singleusergroup/SingleUserGroupTest.java b/src/test/java/com/googlesource/gerrit/plugins/singleusergroup/SingleUserGroupTest.java
index e24db66..89c466b 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/singleusergroup/SingleUserGroupTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/singleusergroup/SingleUserGroupTest.java
@@ -24,8 +24,6 @@
 import com.google.gerrit.extensions.common.GroupInfo;
 import com.google.gerrit.reviewdb.client.AccountGroup;
 import com.google.gerrit.server.IdentifiedUser;
-import com.google.gerrit.server.account.GroupBackend;
-import com.google.inject.Inject;
 import java.util.Map;
 import org.junit.Test;
 
@@ -34,8 +32,6 @@
     name = "singleusergroup",
     sysModule = "com.googlesource.gerrit.plugins.singleusergroup.SingleUserGroup$Module")
 public class SingleUserGroupTest extends LightweightPluginDaemonTest {
-  @Inject private GroupBackend groupBackend;
-
   @Test
   public void testSuggestion() throws Exception {
     // No ability to modify account and therefore no ACL to see secondary email