update trigger project workflow (MetOffice#186)

Co-authored-by: Jenny Hickson <61183013+jennyhickson@users.noreply.github.com>

Author: james-bruten-mo

.github/workflows/trigger-project-workflow.yaml

@@ -2,7 +2,7 @@ name: Trigger Review Project
 
 on:
   pull_request_target:
-    types: ["opened", "synchronize", "reopened", "edited", "review_requested", "review_request_removed"]
+    types: ["opened", "synchronize", "reopened", "edited", "review_requested", "review_request_removed", "closed"]
   pull_request_review:
   pull_request_review_comment: