Remove deprecated Maniphest "Can Edit <Specific Property>" capabilities

Summary:
Depends on D19579. Fixes T10003. These have been deprecated with a setup warning about their impending removal for about two and a half years.

Ref T13164. See PHI642. My overall goal here is to simplify how we handle transactions which have special policy behaviors. In particular, I'm hoping to replace ApplicationTransactionEditor->requireCapabilities() with a new, more clear policy check.

A problem with requireCapabilities() is that it doesn't actually enforce any policies in almost all cases: the default is "nothing", not CAN_EDIT. So it ends up looking like it's the right place to specialize policy checks, but it usually isn't.

For "Disable", I need to be able to weaken the check selectively (you can disable users if you have the permission, even if you can't edit them otherwise). We have a handful of other edits which work like this (notably, leaving and joining projects) but they're very rare.

Test Plan: Grepped for all removed classes. Edited a Maniphest task.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13164, T10003

Differential Revision: https://secure.phabricator.com/D19581