Disable swift_versions for now.

Alamofire.podspec

@@ -9,7 +9,7 @@ Pod::Spec.new do |s|
   s.source = { :git => 'https://github.com/Alamofire/Alamofire.git', :tag => s.version }
   s.documentation_url = 'https://alamofire.github.io/Alamofire/'
 
-  s.swift_versions = ['3', '4', '4.2']
+  # s.swift_versions = ['3', '4', '4.2']
 
   s.ios.deployment_target = '8.0'
   s.osx.deployment_target = '10.10'