Define wgMFMode as stable for desktop Nearby

Introduced by I3c2b7103782e79c8325719f60649cf7453a3bb5c

Bug: 56154
Change-Id: I91c4764b3704a043ba4dcc35981cdc1be7e9a8e2
(cherry picked from commit 3cee71e65da4d62afc6bd2ed9610d2babf925a32)