Update onDeregistered docs to make capability change expectations clear.

Updating the onDeregistered docs to make it clear that the ImsService
must report any feature capability changes to the framework prior to
de-registration.

Bug: 73076695
Test: Docs only change.
Merged-In: Ib9bc88bfb43670f04c8afde36d0947255399397a
Change-Id: Ib9bc88bfb43670f04c8afde36d0947255399397a
1 file changed