ci: fix github.token

Author: kelly-sovacool

.github/workflows/assign-milestone-issue.yml

@@ -21,5 +21,5 @@ jobs:
           echo "gh issue edit $ISSUE --milestone \"$msname\""
           gh issue edit $ISSUE --milestone "$msname"
         env:
-          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GH_TOKEN: ${{ github.token }}
           ISSUE: ${{ github.event.issue.number }}