Bump RabbitMQ.Client to 6.8.0

The RabbitMQ client introduced a breaking API change in a constructor in 6.8.0:
rabbitmq/rabbitmq-dotnet-client#1438

So this lib needs to be recompiled against the new version of RabbitMQ to be fully compatible.

Author: patrikwlund

src/AddUp.FakeRabbitMQ/AddUp.FakeRabbitMQ.csproj

@@ -28,7 +28,7 @@
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
-    <PackageReference Include="RabbitMQ.Client" Version="6.6.0" />
+    <PackageReference Include="RabbitMQ.Client" Version="6.8.0" />
     <PackageReference Include="SonarAnalyzer.CSharp" Version="9.15.0.81779">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>