Remove PASS lines from baselines - legacy web tests

Pass lines are not significant for run_wpt_tests.py. Remove Pass lines
so that the same baseline format can be used by both run_web_tests.py
and run_wpt_tests.py.

This is also desired for developers as no rebaseline is needed when new
passing subtests are added. Due to this also remove the number of
totoal/pass subtests from the summary line.

Bug: 1481730, 1503321
Change-Id: I10b3855e5545cad153b80a738f7fff392bd6c53d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5047251
Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Commit-Queue: Weizhong Xia <weizhong@google.com>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1227651}