[Code Coverage] Fix invocation of run_web_tests

The flag --batch-size has been removed in https://crrev.com/c/1300236.
This CL removes the flag from coverage.py.

Bug: 915336
Change-Id: I22e5ccd5f10bf55795442f87deda767a4954fd32
Reviewed-on: https://chromium-review.googlesource.com/c/1378812
Commit-Queue: Robert Ma <robertma@chromium.org>
Commit-Queue: Max Moroz <mmoroz@chromium.org>
Reviewed-by: Max Moroz <mmoroz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616827}
1 file changed