Replaced (UTC) with %Z

Replaced (UTC) with %Z

I've changed as suggested in https://github.com/StevenBlack/hosts/pull/836#issuecomment-440452979 by @funilrys

The reason I choose NOT to convert this into ISO-8601 is, that we read date.time in different ways depending on with side on the pond we live. By using the "%d %B %Y %H:%M:%S (%Z)" Full date/time this issue is eliminated  and any confusion on how to read the date is no longer existent. The ISO-8601 is good for active pages, as the date ordering is to be manipulated by interface.

Alternative to this is we should add extra lines/info about the date.time ordering, do to this i found this as the easiest way to give this information