Update API documentation per api-council feedback.

Test: SMS/MMS sending/receiving sanity (manual)
Bug: 149236716
Merged--in: I59b9d468fa6e1a5843871abf1a330962aef64505
Change-Id: I59b9d468fa6e1a5843871abf1a330962aef64505
(cherry picked from commit d42340b66cab46f59902bc9f2c57131361612c50)
1 file changed