Update dotnet.yml

.github/workflows/dotnet.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        dotnet-version: [ '8.0.x' ]
+        dotnet-version: [ '6.0.x' ]
         os: [windows-latest, ubuntu-latest, macos-latest]
 
     steps: