Remove waffle serving URL path

[smithellis]

This early pattern is no longer needed.

[akatsoulas]

Why isn't this needed?

[smithellis]

I'm not sure why it was ever there - I think the idea early on was to test some WT stuff at /wagtail, but we have not been doing that. When I asked @escattone about it a while back he agreed that it wasn't really serving a purpose right now.

[akatsoulas]

From what I recall, it was an extra mechanism to control whether WT is enabled in production. If this is the case, I would argue to keep it around until we are ready to go live

[smithellis]

Just to note my thoughts here - we aren't using this right now, so I'd argue it doesn't need to be here. It only allows us to serve things at /wagtail and then only when a waffle flag is set. As far as I know, we are not planning to serve anything at /wagtail at the moment, nor do we use the waffle flag to control wagtail on/off. The login and/or CMS admin is not at /wagtail nor are any pages we are serving.
In another PR I have a more general setting WAGTAIL_ENABLE which does this.
I don't think it makes sense to have unused code (with no known future use) hanging around.