ci: Using .NET 7.0 as the compilation backend.

.github/workflows/dotnet.yml

@@ -20,7 +20,7 @@ jobs:
       - name: Setup .NET
         uses: actions/setup-dotnet@v2
         with:
-          dotnet-version: 6.0.x
+          dotnet-version: 7.0.x
       - name: Restore dependencies
         run: dotnet restore
       - name: Publish