Update dotnet.yml .net 8

Author: d2phap

.github/workflows/dotnet.yml

@@ -23,7 +23,7 @@ jobs:
     - name: Setup .NET
       uses: actions/setup-dotnet@v3
       with:
-        dotnet-version: 6.0.x
+        dotnet-version: 8.0.x
     - name: Restore dependencies
       run: dotnet restore
     - name: Build