android: start proximity sensor anyway

Proximity sensor should be enabled anyway, but only turn screen off when audio is
routing to earpiece while proximity is in `is near` state.

This is for app which can implement `choose audio route` functionality. If a
user start a video call but then wants to use earpiece to continue the
rest conversation, app should be able to route audio to EarPiece and
`turn screen off` while user put their ear close to screen.

Author: zxcpoiu

android/src/main/java/com/zxcpoiu/incallmanager/InCallManagerModule.java

@@ -643,10 +643,7 @@ private void startEvents() {
         startWiredHeadsetEvent();
         startNoisyAudioEvent();
         startMediaButtonEvent();
-        if (!defaultSpeakerOn) {
-            // video, default disable proximity
-            startProximitySensor();
-        }
+        startProximitySensor(); // --- proximity event always enable, but only turn screen off when audio is routing to earpiece.
         setKeepScreenOn(true);
     }