Update GMA iOS Dependency to 9.7.0 (#1040)

Update the Google Mobile Ads dependency to 9.7.0.
Fixed an ambiguous selector to in the AdView implementation on iOS.

Author: DellaBitta

gma/integration_test/Podfile

@@ -5,7 +5,7 @@ use_frameworks! :linkage => :static
 
 target 'integration_test' do
   pod 'Firebase/Analytics', '9.3.0'
-  pod 'Google-Mobile-Ads-SDK', '9.4.0'
+  pod 'Google-Mobile-Ads-SDK', '9.7.0'
 end
 
 post_install do |installer|

gma/src/ios/ad_view_internal_ios.mm

@@ -123,7 +123,7 @@
       ad_load_callback_data_ = nil;
     } else {
       // Make the AdView ad request.
-      [ad_view_ loadRequest:ad_request];
+      [(GADBannerView*)ad_view_ loadRequest: ad_request];
     }
   });
   return future;

ios_pod/Podfile

@@ -5,7 +5,7 @@ use_frameworks!
 target 'GetPods' do
   pod 'Firebase/Core', '9.3.0'
 
-  pod 'Google-Mobile-Ads-SDK', '9.4.0'
+  pod 'Google-Mobile-Ads-SDK', '9.7.0'
   pod 'Firebase/Analytics', '9.3.0'
   pod 'Firebase/Auth', '9.3.0'
   pod 'Firebase/Crashlytics', '9.3.0'

release_build_files/readme.md

@@ -248,7 +248,7 @@ Firebase Functions         | firebase_functions.xcframework
 Google Mobile Ads          | firebase_gma.xcframework
 |                          | firebase.xcframework
 |                          | Firebase/Analytics Cocoapod (9.3.0)
-|                          | Google-Mobile-Ads-SDK Cocoapod (9.4.0)
+|                          | Google-Mobile-Ads-SDK Cocoapod (9.7.0)
 Firebase Installations     | firebase_installations.xcframework
 |                          | firebase.xcframework
 |                          | FirebaseInstallations Cocoapod (9.3.0)
@@ -316,7 +316,7 @@ Firebase Functions         | libfirebase_functions.a
 Google Mobile Ads          | libfirebase_gma.a
 |                          | libfirebase_app.a
 |                          | Firebase/Analytics Cocoapod (9.3.0)
-|                          | Google-Mobile-Ads-SDK Cocoapod (9.4.0)
+|                          | Google-Mobile-Ads-SDK Cocoapod (9.7.0)
 Firebase Installations     | libfirebase_installations.a
 |                          | libfirebase_app.a
 |                          | FirebaseInstallations Cocoapod (9.3.0)
@@ -639,6 +639,7 @@ code.
     - General (Desktop): Fixed an issue with embedded dependencies that could
       cause duplicate symbol linker errors in conjunction with other libraries
       ([#989](https://github.com/firebase/firebase-cpp-sdk/issues/989)).
+    - GMA (iOS): Updated iOS dependency to Google Mobile Ads SDK version 9.7.0.
 
 ### 9.3.0
 -   Changes