Proximity Auth: Clean up unused cruft from ProxAuthSystem.

R=khorimoto@chromium.org

Bug: 899324
Test: none
Change-Id: I997296b1712ddebfe3ceacc69aa25e8b5fed4395
Reviewed-on: https://chromium-review.googlesource.com/c/1330835
Commit-Queue: James Hawkins <jhawkins@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607079}
3 files changed