.rubocop.yml: Lint/SpaceBeforeFirstArg has the wrong namespace - should be Style

[Stephenson131313]

          .rubocop.yml: Lint/SpaceBeforeFirstArg has the wrong namespace - should be Style

Error: The Style/TrailingComma cop no longer exists. Please use Style/TrailingCommaInLiteral and/or Style/TrailingCommaInArguments instead.
(obsolete configuration found in /Users/mmiller/Projects/federal_register/.rubocop.yml, please update it)

Originally posted by @Stephenson131313 in #9 (comment)