[nearby] Update README

Test: n/a
Ignore-AOSP-First: nearby_not_in_aosp_yet
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:99c18f649c9a2623c905f9cbfea04a2559756050)
Merged-In: I0802e60f60170b3be686fa7b16aeb6a2571a7386
Change-Id: I0802e60f60170b3be686fa7b16aeb6a2571a7386
1 file changed