Adapt to Branch.NameKey refactoring

Change-Id: Icba8d5d0193c52ecde4f8692b72471f4d88e82f5
diff --git a/src/main/java/com/googlesource/gerrit/plugins/hooks/Submit.java b/src/main/java/com/googlesource/gerrit/plugins/hooks/Submit.java
index 7474553..ca97ee4 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/hooks/Submit.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/hooks/Submit.java
@@ -49,7 +49,7 @@
 
     HookArgs args = hookFactory.createArgs();
     args.add("--project", projectName);
-    args.add("--branch", destBranch.get());
+    args.add("--branch", destBranch.branch());
     args.add("--submitter", caller.getNameEmail());
     args.add("--submitter-username", caller.getUserName().get());
     args.add("--patchset", patchSetId.get());