webkit-layout-tests: Revert accidental addition of duplicate virtual tests

The patch "Add wpt/css/CSS2/positioning LayoutNG virtual test suite
(patchset #2 id:20001 of https://codereview.chromium.org/2823223004/ )"
accidentally added the "external/wpt/css/CSS2/abspos" and
"external/wpt/css/CSS2/normal-flow" directory to the virtual suite
twice.

This causes layout tests on swarming to fail because the tests are then
run on two different shards making it impossible to merge the results.

This patch removes the second addition.

TBR=atotic@chromium.org,ikilpatrick@chromium.org,glebl@chromium.org,qyearsley@chromium.org,mcgreevy@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=635619,713525

Review-Url: https://codereview.chromium.org/2831053002
Cr-Commit-Position: refs/heads/master@{#465920}
1 file changed