Timer: Ensure the timer thread is deleted before any static or global destructors run

In cases where there was a static or global instance of a class that
inherited from Timer, due to the order of events when a dll is unloaded
on windows, there was a risk of an infinite hang. Deleting the timer
thread before the dll is unloaded avoids this occurring.

modules/juce_events/timers/juce_Timer.h

@@ -141,7 +141,6 @@ private:
     class TimerThread;
     size_t positionInQueue = (size_t) -1;
     int timerPeriodMs = 0;
-    SharedResourcePointer<TimerThread> timerThread;
 
     Timer& operator= (const Timer&) = delete;
 };