build: fix update action on forked repos (ikatyang#653)

Author: thcrack

.github/workflows/update.yml

@@ -20,7 +20,7 @@ jobs:
           git config --global user.name "github-actions[bot]"
           git config --global user.email "41898282+github-actions[bot]@users.noreply.github.com"
           git commit -m "docs(readme): update emoji-cheat-sheet"
-          git push -qf "https://${{ secrets.GITHUB_TOKEN }}@github.com/ikatyang/emoji-cheat-sheet.git" HEAD:github-actions-auto-update
+          git push -qf "https://${{ secrets.GITHUB_TOKEN }}@github.com/${{ github.repository }}.git" HEAD:github-actions-auto-update
 
       - name: Create PR from Updated Branch
         uses: actions/github-script@v2