Add missing GDT dep to MLDownloader (#7675)

Author: paulb777

FirebaseMLModelDownloader.podspec

@@ -38,6 +38,7 @@ Pod::Spec.new do |s|
   s.framework = 'Foundation'
   s.dependency 'FirebaseCore', '~> 7.6'
   s.dependency 'FirebaseInstallations', '~> 7.6'
+  s.dependency 'GoogleDataTransport', '~> 8.3'
   # TODO: Revisit this dependency
   s.dependency 'GoogleUtilities/Logger', '~> 7.2'
   s.dependency 'SwiftProtobuf', '~> 1.0'

FirebaseMLModelDownloader/Apps/Sample/Podfile

@@ -1,6 +1,10 @@
 platform :ios, '10.0'
 use_frameworks!
 
+source 'https://github.com/firebase/SpecsDev.git'
+source 'https://github.com/firebase/SpecsStaging.git'
+source 'https://cdn.cocoapods.org/'
+
 pod 'FirebaseMLModelDownloader', :path => '../../../'
 pod 'TensorFlowLiteSwift'