Removes audio_queue_.flush() calls; I don't think I really need to block. At least, not usually.

Machines/Atari/2600/Cartridges/Cartridge.hpp

@@ -201,7 +201,6 @@ template<class T> class Cartridge:
 			update_audio();
 			update_video();
 			audio_queue_.perform();
-			audio_queue_.flush();
 		}
 
 	protected:

Machines/ColecoVision/ColecoVision.cpp

@@ -360,7 +360,6 @@ class ConcreteMachine:
 			vdp_.flush();
 			update_audio();
 			audio_queue_.perform();
-			audio_queue_.flush();
 		}
 
 		float get_confidence() override {

Machines/MSX/MSX.cpp

@@ -618,7 +618,6 @@ class ConcreteMachine:
 			vdp_.flush();
 			update_audio();
 			audio_queue_.perform();
-			audio_queue_.flush();
 		}
 
 		void set_keyboard_line(int line) {

Machines/MasterSystem/MasterSystem.cpp

@@ -342,7 +342,6 @@ class ConcreteMachine:
 			vdp_.flush();
 			update_audio();
 			audio_queue_.perform();
-			audio_queue_.flush();
 		}
 
 		const std::vector<std::unique_ptr<Inputs::Joystick>> &get_joysticks() override {