Add documentation for what to use for SS changes

Since the broadcast is deprecated in favor of the ServiceStateProvider,
the documentation should reflect this.

Note that the LteEarfcnRsrpBoost has not been migrated into the provider
so this also needs to happen.

Bug: 33756364
Fixes: 78188866
Test: no behavior change, ran make
Change-Id: Ia15a7408bdc79927438fa243cce77b262bbb66c4