Delete FinancialSmsService and friends.

This feature is incomplete and non functional and there
appear to be no plans to complete it.

Note that the removal of the SystemApi is safe because the
class was designed for extension but didn't have a public
constructor, rendering it unusable as an API.

Test: make
Bug: 138589409

Change-Id: Iadd0da93495cb9bef09aa2fee4514302d3212eb0