[CodeQL] Setup .NET 6

Author: i4004

.github/workflows/codeql-analysis.yml

@@ -51,6 +51,11 @@ jobs:
           # Prefix the list here with "+" to use these queries and those in the config file.
           # queries: ./path/to/local/query, your-org/your-repo/queries@main
 
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v1
+        with:
+          dotnet-version: 6.0.x
+
       # Build
       - run: dotnet build src/Simplify.sln -v minimal