setup .net7 for benchmark

Author: Meir017

.github/workflows/benchmark.yml

@@ -16,6 +16,10 @@ jobs:
         uses: actions/setup-dotnet@v4
         with:
           dotnet-version: '6.x'
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '7.x'
       - name: Run benchmark
         run: cd src/FluentAssertions.Analyzers.BenchmarkTests && dotnet run -c Release --exporters json --filter '*'