fix: Remove Google Mobile Ads SDK

[jonnyandrew]

Problem

The library includes the full Google Mobile Ads SDK in order to access the Android Advertising ID (AAID). This causes a crash when including Parse.ly as the Ads library expects to be initialised with an AdMob app ID.

Example crash log

java.lang.RuntimeException: Unable to get provider com.google.android.gms.ads.MobileAdsInitProvider: java.lang.IllegalStateException: 
    
    ******************************************************************************
    * The Google Mobile Ads SDK was initialized incorrectly. AdMob publishers    *
    * should follow the instructions here:                                       *
    * https://googlemobileadssdk.page.link/admob-android-update-manifest         *
    * to add a valid App ID inside the AndroidManifest.                          *
    * Google Ad Manager publishers should follow instructions here:              *
    * https://googlemobileadssdk.page.link/ad-manager-android-update-manifest.   *
    ******************************************************************************

Solution

Replace the full Google Mobile Ads SDK with the Advertising ID library which includes only what's needed by the Parse.ly code.

[wzieba]

Looks good to me, thank you!