Update Geolocation.js

Summary:
Clearer wording, on first read it is possible to get the impression that it will return immediately for both cached and on update request.
Closes https://github.com/facebook/react-native/pull/12072

Differential Revision: D4482784

Pulled By: mkonicek

fbshipit-source-id: 9eb9acf946b97b7b2b51f07e6a6572098afe7610

Libraries/Geolocation/Geolocation.js

@@ -61,8 +61,8 @@ var Geolocation = {
   /*
    * Invokes the success callback once with the latest location info.  Supported
    * options: timeout (ms), maximumAge (ms), enableHighAccuracy (bool)
-   * On Android, this can return almost immediately if the location is cached or
-   * request an update, which might take a while.
+   * On Android, if the location is cached this can return almost immediately,
+   * or it will request an update which might take a while.
    */
   getCurrentPosition: function(
     geo_success: Function,