Removing getAnonymousDevice

ag/15933623 remove the need to call setAttributionSource.
This CL aim to clean the getAnonymousDevice method that was left over

Bug: 195144968
Tag: #refactor
Test: build
Ignore-AOSP-First: No such thing on aosp
Change-Id: I11d82004008188e0075827bdbe741893b655c664