Add @SupressLint to get around incorrect warning.

EthernetNetworkSpecifier is being moved from being @SystemApi to public.
This is causing the linter to incorrectly throw errors when building on
erro prone. Add @SupressLint to the method causing the errors prevents
the incorrect warning from causing build failures.

Tracking bug b/193460475 - TODO to remove once fixed.

cherry pick of http://ag/16822701

Bug: 210485380
Test: build errorprone
Change-Id: Id297e739a2288ccc232c6b989ec7fee41837a910
Merged-In: Id297e739a2288ccc232c6b989ec7fee41837a910