autotest: Remove network_WiFi_Netperf and derivative tests

Recent investigation into our testing methodology reveals that
performance tests in regular WiFi cells are overly sensitive to
little physical configuration differences like the relative positions of
the antenna and DUT.  This can cause dramatic differences in measured
throughput that invalidates negative results.  In addition, high
throughput could indicate that we're merely using a higher symbol rate
rather than taking advantage of frame aggregation.

BUG=chromium:271511
TEST=None

Change-Id: If5349b35969ec1a0a786fa4e2e4a7723d5a009e0
Reviewed-on: https://gerrit.chromium.org/gerrit/65610
Tested-by: Christopher Wiley <wiley@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
Commit-Queue: Christopher Wiley <wiley@chromium.org>
3 files changed