[spec] framework .NET 9 set

Author: i4004

.github/workflows/codeql-analysis.yml

@@ -54,7 +54,7 @@ jobs:
       - name: Setup .NET
         uses: actions/setup-dotnet@v4
         with:
-          dotnet-version: 8.0.x
+          dotnet-version: 9.0.x
 
       # Build
       - run: dotnet build src/Simplify.Web.sln -v minimal