cellular: remove legacy network_3GLoadFirmware test

This test no longer works as the legacy scripts it depends on have been
removed. We will instead add generic power cycle and suspend/resume
tests that work for all supported modems.

BUG=None
TEST=Remote trybot runs on paladin builders.

Change-Id: I5b8e25792a9c8275010fb5acc1bb47a4e182cae6
Reviewed-on: https://chromium-review.googlesource.com/185914
Reviewed-by: Thieu Le <thieule@chromium.org>
Commit-Queue: Ben Chan <benchan@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
5 files changed