Remove experimental GDK ruby_services setting

What does this Merge Request do?

!1230 (merged) brought in the gdk.experimental settings namespace but it also accidentally brought in the gdk.experimental.ruby_services setting (and some logic in !1196 (merged)) which really should be included only as part of !1197 (merged).

If one sets gdk.experimental.ruby_services now, it will result in no services being available which is obviously a bad thing.

This MR removes gdk.experimental.ruby_services and logic from master until it's ready.

Merge Request checklist

• Tests added for new functionality. If not, please raise Issue to follow-up.
• This change is backward compatible. If not, please include steps to communicate to our users.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.