• Updates GMA Android dependency to 21.0.0 and iOS to 9.6.0
• Removes credentials from AdapterResponseInfo, which is replaced with adUnitMapping.
• Removes serverSideVerificationOptions from RewardedAd.load() and RewardedInterstitialAd.load(), replacing them with setters
  RewardedAd.setServerSideVerificationOptions() and RewardedInterstitialAd.setServerSideVerificationOptions(). This lets you
  update the ssv after the ad is loaded.
• Removes static testAdUnitId parameters. See the Admob and
  AdManager documentation for up to date test ad units.
• Removes NativeAdListener.onNativeAdClicked. You should use onAdClicked instead, which present on all ad listeners.
• Removes AdRequest.location