Revert "Change unassign action to use koppor's patch"

This reverts commit 06530d8.

Author: koppor

.github/workflows/unassign-issues.yml

@@ -16,7 +16,7 @@ jobs:
     steps:
       - name: Unassign stale assignments
         id: unassign
-        uses: koppor/assign-issue-action@patch-2
+        uses: takanome-dev/assign-issue-action@edge
         with:
           github_token: '${{ secrets.GITHUB_TOKEN }}'
           reminder_comment: |