Proximity Auth: Remove kMultiDeviceApi flagging from ProximityAuthSystem.

R=hansberry@chromium.org

Bug: 899324
Test: none
Change-Id: I0738957fbcdb63da03152d852cf20e02603f7924
Reviewed-on: https://chromium-review.googlesource.com/c/1325429
Commit-Queue: James Hawkins <jhawkins@chromium.org>
Reviewed-by: Ryan Hansberry <hansberry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606518}
1 file changed