This guard blocks main loop.

And I've been told that by design the main thread doesn't need to be
aware of the rendering threads, so no need to take mutex here.

Change-Id: I78ec348ccc28dd67284ecdfccebb915cc1942fa8

chart2/source/view/charttypes/GL3DBarChart.cxx

@@ -1176,7 +1176,6 @@ int GL3DBarChart::calcTimeInterval(TimeValue &startTime, TimeValue &endTime)
 void GL3DBarChart::updateScreenText()
 {
     SharedResourceAccess(maCond1, maCond2);
-    osl::MutexGuard aGuard(maMutex);
     maScreenTextShapes.clear();
     mpRenderer->ReleaseScreenTextShapes();
     updateRenderFPS();