Fix leak in input-color-under-shadow-popup-crash.html

My HTML parser change for <select> here caused the resulting DOM of this
test to change:
https://chromium-review.googlesource.com/c/chromium/src/+/5518837

This patch adds a </select> end tag to make the test have the same DOM
structure as before my change.

I verified that the test would have also leaked without my parser change
by manually appending the <input> to the <select> on a commit before the
parser change was merged.

Change-Id: Icbacbf6967dc3aa8725a22b814729301bc38abef
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5719475
Reviewed-by: David Baron <dbaron@chromium.org>
Auto-Submit: Joey Arhar <jarhar@chromium.org>
Commit-Queue: David Baron <dbaron@chromium.org>
Commit-Queue: Joey Arhar <jarhar@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1329238}