Global namespaces for ruby basic types (#6418)

File here will be overriden by generated class File of swagger.yml containse the definition named File. Using global namespace can fix it

modules/swagger-codegen/src/main/resources/ruby/api_client.mustache

@@ -274,7 +274,7 @@ module {{moduleName}}
         data = {}
         form_params.each do |key, value|
           case value
-          when File, Array, nil
+          when ::File, ::Array, nil
             # let typhoeus handle File, Array and nil parameters
             data[key] = value
           else