remove activation button from preferred NW setting

- platform today only supports hands-free activation, otasp activation
  automatically starts at background (non-interactive call),
  no user interaction is required.
- activation button will trigger deprecated ActivationActivity inside
  SuW which we plan to remove for a long time.
- the activation button itself is buggy, it only shows from the cdma
  menu if it is running on tablets and cdma-only device which is
  inconsist with logics from elsewhere.

Bug: 33784603
Test: manual testing
Change-Id: I281ffc475f53c8ea7b1cd4a2cfc573ad66b5b88d
3 files changed