Fix Xcode 10.2 warning about Test project.
Fix Xcode 10.2 warning about Test project.

Use the specifier `en` instead of `English` as with the commit(d306ba88173ebfd25f93e0114e0bff06e03fd416).

CocoaLumberjack/CocoaLumberjack,CocoaLumberjack/CocoaLumberjack,jum/CocoaLumberjack,sushichop/CocoaLumberjack,sushichop/CocoaLumberjack,CocoaLumberjack/CocoaLumberjack,sushichop/CocoaLumberjack,sushichop/CocoaLumberjack,jum/CocoaLumberjack,jum/CocoaLumberjack,CocoaLumberjack/CocoaLumberjack,jum/CocoaLumberjack