Update dotnetcore-build.yml to install .NET 9.0.x SDK for pipeline run

Author: pbhal

.github/workflows/dotnetcore-build.yml

@@ -14,7 +14,7 @@ jobs:
     - name: Setup .NET Core
       uses: actions/setup-dotnet@v4
       with:
-        dotnet-version: 8.0.x
+        dotnet-version: 9.0.x
 
     - name: Install dependencies
       run: dotnet restore RulesEngine.sln