[Tagging] Remove non-prefixed versions of 'contact:' scheme

[s8evq]

Hi Paul,

On Mon, 11 May 2020 02:10:12 +0100, Paul Allen <pla16021 at gmail.com> wrote:
> I find the whole contact: namespace to be ill-conceived.  But fine, if
> you want it then use it.  Just please stop suggesting that we
> deprecate website=* and phone=*.

What's you counter argument to the people suggesting that contact:* makes it easier for data consumers to gather all contact info in one go, instead of hard coding all the possible keys. What if next year a new way of contacting comes up?