Remove clean-check requirement from gate

OpenStack adopted a clean-check requirement for its gate pipeline
(i.e., a change must pass check before being enqueued into gate).
If that is not desired in the kata-containers tenant, this change
will remove it.

Change-Id: Ib24a33031023f7c20d36ae3c21a27bb8d626cf36

zuul.d/pipelines.yaml

@@ -22,12 +22,6 @@
         - event: change-restored
         - event: comment-added
           comment: (?i)^(Patch Set [0-9]+:)?( [\w\\+-]*)*(\n\n)?\s*recheck
-        - event: comment-added
-          require-approval:
-            - Verified: [-1, -2]
-              username: zuul
-          approval:
-            - Workflow: 1
       github:
         - event: pull_request
           action:
@@ -73,19 +67,13 @@
       gerrit:
         open: True
         current-patchset: True
-        approval:
-          - Verified: [1, 2]
-            username: zuul
-          - Workflow: 1
     trigger:
       gerrit:
         - event: comment-added
           approval:
             - Workflow: 1
         - event: comment-added
-          approval:
-            - Verified: 1
-          username: zuul
+          comment: (?i)^(Patch Set [0-9]+:)?( [\w\\+-]*)*(\n\n)?\s*reverify
     start:
       gerrit:
         Verified: 0