Fix path of AirMapModule

The PR that added `AirMapModule` (react-native-maps#449) was merged after the PR that
moved all the `lib/src/*` files to just `src/*` (react-native-maps#502). Fix it by moving
`AirMapModule` to `src/`.

Author: Spike Brehm

android/src/main/java/com/airbnb/android/react/maps/AirMapManager.java

@@ -1,7 +1,6 @@
 package com.airbnb.android.react.maps;
 
 import android.view.View;
-import android.content.Context;
 
 import com.facebook.react.bridge.Arguments;
 import com.facebook.react.bridge.ReactApplicationContext;