Remove TimelineTraceManager::State

This is redundant, now that we have registerFeatures().

Change-Id: Ia56c28b8892ab6da694570fe4b9ea5c96fe194f1
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/qmlprofiler/tests/debugmessagesmodel_test.cpp

@@ -53,7 +53,6 @@ void DebugMessagesModelTest::initTestCase()
         manager.addEvent(event);
     }
     manager.finalize();
-    QCOMPARE(manager.state(), QmlProfilerModelManager::Done);
 }
 
 void DebugMessagesModelTest::testTypeId()