Switch tox-github-action from master to main branch

See #24

Author: frenzymadness

.github/workflows/main.yml

@@ -15,7 +15,7 @@ jobs:
     - uses: actions/checkout@v2
     - name: Run Tox tests
       id: test
-      uses: fedora-python/tox-github-action@master
+      uses: fedora-python/tox-github-action@main
       with:
         tox_env: ${{ matrix.tox_env }}
     strategy: