ci: use major version (#491)

Author: uiolee

.github/workflows/tester.yml

@@ -45,6 +45,6 @@ jobs:
         env:
           CI: true
       - name: Coveralls
-        uses: coverallsapp/github-action@master
+        uses: coverallsapp/github-action@v2
         with:
           github-token: ${{ secrets.github_token }}