IMS: Do not downgrade the video call for mobile data off when video pause is supported

- This change is required because we have provided the downgrade capabilities
  for video calls by default for internal targets due to a requirement
  for testing downgrade to voice irrespective of whether carrier supports it

- The above change breaks functionality right now for the use case where
  mobile data is off and we handover from WIFI to LTE. Current code only
  checks for downgrade capabilities which is there for all carriers on
  internal targets

- The fix is to only downgrade the call if the carrier doesn't support Video
  pause.

Test: Manual
Bug: 76404479
Change-Id: Ie27d955516c104d7bda2fbf77dcdb8acac449feb