update action

Author: ChristianSauer

.github/workflows/action.yml

@@ -11,10 +11,9 @@ jobs:
         uses: actions/setup-dotnet@v3
         with:
           dotnet-version: |
-            5
-            6
             7
             8
+            9
       - name: Install dependencies
         run: dotnet restore
       - name: Build