Fix Pull Request import due to TimeUtil moved to another package

TimeUtil has been moved in Gerrit-2.11/master to another package
(com.google.gerrit.common) and thus needs to be updated.

Change-Id: I28473e7056875f9472c527279eba164d87d18ef1
diff --git a/github-plugin/src/main/java/com/googlesource/gerrit/plugins/github/git/PullRequestCreateChange.java b/github-plugin/src/main/java/com/googlesource/gerrit/plugins/github/git/PullRequestCreateChange.java
index 52be75c..9025e9c 100644
--- a/github-plugin/src/main/java/com/googlesource/gerrit/plugins/github/git/PullRequestCreateChange.java
+++ b/github-plugin/src/main/java/com/googlesource/gerrit/plugins/github/git/PullRequestCreateChange.java
@@ -60,6 +60,7 @@
 import com.google.gerrit.server.project.ProjectControl;
 import com.google.gerrit.server.project.RefControl;
 import com.google.gerrit.server.ssh.NoSshInfo;
+import com.google.gerrit.common.TimeUtil;
 import com.google.gwtorm.server.OrmException;
 import com.google.gwtorm.server.ResultSet;
 import com.google.inject.Inject;