fix whitespace

Author: KyFaSt

lib/secure_headers/headers/content_security_policy.rb

@@ -55,7 +55,7 @@ def build_value
         case DIRECTIVE_VALUE_TYPES[directive_name]
         when :source_list,
              :require_sri_for_list, # require_sri is a simple set of strings that don't need to deal with symbol casing
-             :require_trusted_types_for_list 
+             :require_trusted_types_for_list
           build_source_list_directive(directive_name)
         when :boolean
           symbol_to_hyphen_case(directive_name) if @config.directive_value(directive_name)