Expose audio_jitter_buffer_fast_accelerate config to objc wrapper

NOTRY=True
BUG=webrtc:6827

Review-Url: https://codereview.webrtc.org/2556553002
Cr-Commit-Position: refs/heads/master@{#15429}

webrtc/sdk/objc/Framework/Headers/WebRTC/RTCConfiguration.h

@@ -84,6 +84,7 @@ RTC_EXPORT
 @property(nonatomic, assign)
     RTCContinualGatheringPolicy continualGatheringPolicy;
 @property(nonatomic, assign) int audioJitterBufferMaxPackets;
+@property(nonatomic, assign) BOOL audioJitterBufferFastAccelerate;
 @property(nonatomic, assign) int iceConnectionReceivingTimeout;
 @property(nonatomic, assign) int iceBackupCandidatePairPingInterval;