Remove unused class DiceTestTokenServiceObserver

This is a left over of https://crrev.com/c/1355189 ([signin] Delete
DiceFixAuthErrors).

TBR=droger@chromium.org

BUG= 777774

Change-Id: I89b6359df1c8910973ca3bcdc9c9145b89d5d464
Reviewed-on: https://chromium-review.googlesource.com/c/1394666
Reviewed-by: David Roger <droger@chromium.org>
Reviewed-by: Antonio Gomes <tonikitoo@igalia.com>
Commit-Queue: Antonio Gomes <tonikitoo@igalia.com>
Cr-Commit-Position: refs/heads/master@{#619914}
1 file changed