Don't comment in Gerrit when changes are dequeued

Change-Id: Idb8a5e33b990743ca9f3bb85098889c224130424
diff --git a/zuul.d/pipelines.yaml b/zuul.d/pipelines.yaml
index e018b08..c2fcb76 100644
--- a/zuul.d/pipelines.yaml
+++ b/zuul.d/pipelines.yaml
@@ -33,6 +33,7 @@
           message: 'No jobs were triggered'
     dequeue:
       gerrit:
+        comment: False
         checks-api:
           scheme: 'zuul-check'
           state: NOT_RELEVANT