fix: keep the log handler set by the brokerage test project

- stop replacing it with NUnitLogHandler on every test
- brokerage test projects keep their file log for the whole run

Author: Romazes

Tests/Brokerages/BrokerageTests.cs

@@ -50,8 +50,6 @@ public abstract class BrokerageTests
         [SetUp]
         public void Setup()
         {
-            Log.LogHandler = new NUnitLogHandler();
-
             Log.Trace("");
             Log.Trace("");
             Log.Trace("--- SETUP ---");