Replace issue.number with pr.number i survey-on-merged-pr.yml

One more fix... hope this time it works ;-)

Author: svrnm

.github/workflows/survey-on-merged-pr.yml

@@ -5,7 +5,7 @@ on:
     types: [closed]
 
 env:
-  PR_NUM: ${{ github.event.issue.number }}
+  PR_NUM: ${{ github.event.pull_request.number }}
   SURVEY_URL: https://forms.gle/WV58koUBGSG9HBY66
 
 jobs: