Effectively remove EDIT_DEFER_UPDATES flag

Effectively remove EDIT_DEFER_UPDATES flag

* All DeferrableUpdates will be deferred as normal.
  In CLI mode this is just post-commit and would have
  happened before the doUpdates() call anyway. For web
  requests this will be at request-end (post-send on HHVM).
  Note that deferral was already the default for EditPage.
* Previously, it was easy to accidently not set EDIT_DEFER_UPDATES.
  Deferred updates are supposed to be deferrable by definition,
  and there is no longer the problem of them piling up in CLI in
  recent versions. Not deferring mostly just forfeits performance.
* Also, it is not really the responsibility of WikiPage to be
  running DeferrableUpdate instances itself.

Change-Id: I2bc47b82635e0a24b1df5d502ba66f6de737697e