merge_pr_50273

wpt: Fix references for /css/CSS2/tables/table-anonymous-objects-*

Some of these tests were using no_red_3x3_monospace_table-ref.xht as
a reference. However, the reference has a single 3x3 table, while the
tests put each row on a different table. Thus text wasn't aligning well,
and the tests were failing on all browsers. Therefore this adds a new
reference for these tests.

Some other tests were instead adding a background on their columns.
These also get their own reference. But additionally, these tests
attempt to work as visual tests by overlapping two tables: one with
green text in front of another with red text. However, this feature
was broken since both tables had a background, so the underlying one
was not visible at all.
Therefore, I'm also removing the background of the table at the front.
Note that these tests come in pairs that just switch which one is in
front, so no functionality is lost.

Signed-off-by: Oriol Brufau [email protected]