revert benchmark script to .net 8

Author: Yannis-S-Standaert

.github/workflows/benchmark.yml

@@ -39,7 +39,7 @@ jobs:
             - name: Set up .NET
               uses: actions/setup-dotnet@v2
               with:
-                  dotnet-version: "9.0.x" # Adjust based on your target framework
+                  dotnet-version: "8.0.x" # Adjust based on your target framework
 
             - name: Install k6
               run: |