doc: fix track event namespace

doc/API.md

@@ -148,7 +148,7 @@ JitsiMeetJS.setLogLevel(JitsiMeetJS.logLevels.ERROR);
     3. detection
         - VAD_SCORE_PUBLISHED - event generated by a TackVADEmitter when it computed a VAD score for an audio PCM sample.
 
-    3. tracks
+    3. track
         - LOCAL_TRACK_STOPPED - indicates that a local track was stopped. This
         event can be fired when ```dispose()``` method is called or for other reasons.
         - TRACK_AUDIO_OUTPUT_CHANGED - indicates that audio output device for track was changed (parameters - deviceId (string) - new audio output device ID).