tools: use ref_name to get branch pushed on

.github/workflows/notify-on-push.yml

@@ -20,7 +20,7 @@ jobs:
           SLACK_ICON: https://github.com/nodejs.png?size=48
           SLACK_TITLE: ${{ github.actor }} force-pushed to ${{ github.ref }}
           SLACK_MESSAGE: |
-            @here A commit was force-pushed to <https://github.com/${{ github.repository }}/tree/${{ github.repository.default_branch }}|${{ github.repository }}@${{ github.repository.default_branch }}> by <https://github.com/${{ github.actor }}|${{ github.actor }}>
+            @here A commit was force-pushed to <https://github.com/${{ github.repository }}/tree/${{ github.ref_name }}|${{ github.repository }}@${{ github.ref_name }}> by <https://github.com/${{ github.actor }}|${{ github.actor }}>
 
             Before: <https://github.com/${{ github.repository }}/commit/${{ github.event.before }}|${{ github.event.before }}>
             After: <https://github.com/${{ github.repository }}/commit/${{ github.event.after }}|${{ github.event.after }}>
@@ -62,7 +62,7 @@ jobs:
           SLACK_ICON: https://github.com/nodejs.png?size=48
           SLACK_TITLE: Invalid commit was pushed to ${{ github.repository.default_branch }}
           SLACK_MESSAGE: |
-            @here A commit lacking the expected metadata was pushed to <https://github.com/${{ github.repository }}/tree/${{ github.repository.default_branch }}|${{ github.repository }}@${{ github.repository.default_branch }}> by <https://github.com/${{ github.actor }}|${{ github.actor }}>.
+            @here A commit lacking the expected metadata was pushed to <https://github.com/${{ github.repository }}/tree/${{ github.ref_name }}|${{ github.repository }}@${{ github.ref_name }}> by <https://github.com/${{ github.actor }}|${{ github.actor }}>.
 
             Before: <https://github.com/${{ github.repository }}/commit/${{ github.event.before }}|${{ github.event.before }}>
             After: <https://github.com/${{ github.repository }}/commit/${{ github.event.after }}|${{ github.event.after }}>