Keep swift version

Author: tomlokhorst

R.swift.Library.podspec

@@ -17,7 +17,7 @@ Pod::Spec.new do |spec|
 
   spec.requires_arc = true
   spec.source          = { :git => "https://github.com/mac-cain13/R.swift.Library.git", :tag => "v#{spec.version}" }
-  spec.swift_version   = "5.7"
+  spec.swift_version   = "5.1"
 
   spec.pod_target_xcconfig = { 'APPLICATION_EXTENSION_API_ONLY' => 'YES' }