Fixed the dotnet version in the GitHub script

Author: jasdefer

.github/workflows/dotnetcore.yml

@@ -14,7 +14,7 @@ jobs:
     - name: Setup .NET Core
       uses: actions/setup-dotnet@v1
       with:
-        dotnet-version: 5.0.301
+        dotnet-version: 6.0.302
     - name: Build the solution
       run:
         dotnet build DotnetGraph/ --configuration Release