maint(ios): remove .mobileconfig font installation

[mcdurdin]

We have no keyboards that use .mobileconfig now. The relevant code should be removed from ios source and the corresponding content removed from r.keymanweb.com.

See also:

• feat(ios): iOS 13 supports system-wide font installation, apparently. So we should do that. #3445
• maint: remove legacy .eot, .mobileconfig, .svg fonts and infrastructure r.keymanweb.com#13
• maint: remove 1.0-3.0 legacy cloud endpoints api.keyman.com#359