Change trigger.py with --desugar to not throw assertion after it is done

Change-Id: If73e11d673ed97383e51d749d0d287c3ab5a64bb
diff --git a/tools/trigger.py b/tools/trigger.py
index 5ce6a42..482608a 100755
--- a/tools/trigger.py
+++ b/tools/trigger.py
@@ -105,8 +105,7 @@
     builders = [options.builder]
   if options.desugar:
     builders = [DESUGAR_BOT]
-    trigger_builders(
-        builders, git_utils.GetHeadRevision(utils.REPO_ROOT, use_master=True))
+    commit = git_utils.GetHeadRevision(utils.REPO_ROOT, use_master=True)
   if options.cl:
     trigger_cl(builders, options.cl)
   else: