Merge pull request #474 from grondo/mergify-wip

mergify: fix wip regex

Author: garlick

.mergify.yml

@@ -16,7 +16,7 @@ pull_request_rules:
       - base=master
       - label="merge-when-passing"
       - label!="work-in-progress"
-      - -title~="^\[*(WIP|wip)"
+      - -title~=(?i)^(\[)?wip
       - "approved-reviews-by=@flux-framework/core"
       - "#approved-reviews-by>0"
       - "#changes-requested-reviews-by=0"