Fix windows labeler

Signed-off-by: Maksym Pavlenko <pavlenko.maksym@gmail.com>

.github/workflows/labeler.yml

@@ -16,7 +16,7 @@ jobs:
     # Required by gh
     env:
       GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-      PR_NUMBER: ${{ github.event.number }}
+      PR_URL: ${{ github.event.pull_request.html_url }}
 
     steps:
     - uses: actions/labeler@v4
@@ -27,5 +27,5 @@ jobs:
         sync-labels: true
 
     # Apply OS-windows label if PR title contains 'Windows'
-    - run: gh pr edit $PR_NUMBER --add-label OS-windows
+    - run: gh pr edit $PR_URL --add-label OS-windows
       if: contains(github.event.pull_request.title, 'Windows')