chore(firestore): use precompiled Firestore frameworks again in 4.x example Podfiles (#18865)

invertase/firestore-ios-sdk-frameworks now has a 12.19.3 tag, and FirebaseFirestoreBinary/FirebaseFirestoreInternalBinary 12.19.3 are on CocoaPods trunk.

Author: Lyokone

packages/cloud_firestore/cloud_firestore/example/ios/Podfile

@@ -50,6 +50,8 @@ target 'Runner' do
       raise "Error - unable to locate firebase_ios_sdk.rb script in firebase_core, and no FirebaseSDKVersion specified"
     end
   end
+
+  pod 'FirebaseFirestore', :git => 'https://github.com/invertase/firestore-ios-sdk-frameworks.git', :tag => "#{firebase_sdk_version}"
 end
 
 post_install do |installer|

packages/cloud_firestore/cloud_firestore/example/macos/Podfile

@@ -49,6 +49,8 @@ target 'Runner' do
       raise "Error - unable to locate firebase_ios_sdk.rb script in firebase_core, and no FirebaseSDKVersion specified"
     end
   end
+
+  pod 'FirebaseFirestore', :git => 'https://github.com/invertase/firestore-ios-sdk-frameworks.git', :tag => "#{firebase_sdk_version}"
 end
 
 post_install do |installer|