Remove a wrong win7 specific expected.txt

This file causes a flaky report for virtual/blink-cors.
But, this win7 specific expectation is not consistent to
results in other platforms, and looks just wrong.

If removing this expectation results in other flaky reports,
we should update TestExpectations for them, and file another
bug for them.

Bug: 974710
Change-Id: I258ff80787cab85dc2b1fe4f0e7bf9ee3f0e9868
NOTRY: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1664102
Auto-Submit: Takashi Toyoshima <toyoshim@chromium.org>
Reviewed-by: Karan Bhatia <karandeepb@chromium.org>
Commit-Queue: Karan Bhatia <karandeepb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#670374}