AudioCommon: Remove lock on Pause state

We had to lock audiocommon with the old asynchron HLE audio emulation,
now our Mixer is just a plain FIFO which may underrun.
Of course, this will stutter, but underruning the audio backend is likely worse.

Source/Core/AudioCommon/AudioCommon.h

@@ -17,7 +17,6 @@ namespace AudioCommon
 	SoundStream* InitSoundStream();
 	void ShutdownSoundStream();
 	std::vector<std::string> GetSoundBackends();
-	void PauseAndLock(bool doLock, bool unpauseOnUnlock = true);
 	void UpdateSoundStream();
 	void ClearAudioBuffer(bool mute);
 	void SendAIBuffer(short* samples, unsigned int num_samples);