Fix pipelines - there's no request_changes state

It also expects a list:

The trigger configuration as supplied has an error: expected a list for dictionary value @ data['state']

Author: mnasiadka

zuul.d/pipelines.yaml

@@ -76,13 +76,15 @@
       github:
         - event: pull_request_review
           action: submitted
-          state: approved
+          state:
+            - approved
         - event: pull_request
           action: comment
           comment: (?i)^\s*regate\s*$
         - event: pull_request_review
           action: dismissed
-          state: request_changes
+          state:
+            - changes_requested
         - event: pull_request
           action: status
           status: ".*:success"