Updating podspec to point to public location

Change-Id: I8e07a784c70d94b2fc22f3d22b7d01aa2f8ac1e7

Author: asciimike

FirebaseUI.podspec

@@ -5,7 +5,7 @@ Pod::Spec.new do |s|
   s.homepage     = 'https://github.com/firebase/FirebaseUI-iOS'
   s.license      = { :type => 'Apache License, Version 2.0', :file => 'LICENSE' }
   s.author       = { 'Firebase' => '[email protected]' }
-  s.source       = { :http => 'https://storage.googleapis.com/gcpstatic/FirebaseUIFrameworks.zip' }
+  s.source       = { :http => 'https://dl.google.com/firebase/firebaseui/ios/0_4_0/FirebaseUIFrameworks.zip' }
   s.platform = :ios
   s.ios.deployment_target = '7.0'
   s.ios.framework = 'UIKit'