spaces rather than hyphens in wip label

Author: alecmocatta

.mergify.yml

@@ -3,7 +3,7 @@ pull_request_rules:
     conditions:
       - base=master
       - status-success=tests
-      - label!=work-in-progress
+      - "label!=work in progress"
       - "#approved-reviews-by>=1"
       - "#review-requested=0"
       - "#changes-requested-reviews-by=0"
@@ -17,7 +17,7 @@ pull_request_rules:
     conditions:
       - base=master
       - status-success=tests
-      - label!=work-in-progress
+      - "label!=work in progress"
       - author=alecmocatta # https://github.com/Mergifyio/mergify-engine/issues/451
       - "#review-requested=0"
       - "#changes-requested-reviews-by=0"
@@ -36,10 +36,10 @@ pull_request_rules:
       - "title~=^WIP: .*"
     actions:
       label:
-        add: ["work-in-progress"]
+        add: ["work in progress"]
   - name: auto remove wip label
     conditions:
       - "-title~=^WIP: .*"
     actions:
       label:
-        remove: ["work-in-progress"]
+        remove: ["work in progress"]