Try to fix the linter workflow

Author: gerzse

.github/workflows/linter.yaml

@@ -14,9 +14,7 @@ jobs:
         run: dotnet tool install -g dotnet-format
 
       - name: Checkout repo
-        uses: actions/checkout@v2
-        with:
-          ref: ${{ github.head_ref }}
+        uses: actions/checkout@v3
 
       - name: lint
         run: |