Remove buildbot Nougat Phone Tester from milo

This hasn't had any builds since 04/2018

Bug: 790146
Change-Id: I867b60e3dd9e4250fc739aa4ec13d97f32e65c23
Reviewed-on: https://chromium-review.googlesource.com/c/1475168
Commit-Queue: Brad Hall <bradhall@google.com>
Reviewed-by: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#632676}
1 file changed