WebUI Omnibox: Disable OmniboxPopupTest.App on linux-js-coverage-rel.

DevToolsListener::VerifyAllScriptsAreParsedRepeatedly() seems confused
when multiple instances of the same WebUI exist and throws the following
error

[1380392:1380392:1006/174456.007070:FATAL:chrome/test/base/devtools_listener.cc:156]
Check failed: all_scripts_parsed_. All scripts in coverage results were
not retrieved after 10s of waiting

This likely happens because chrome://omnibox-popup.top-chrome is loaded
twice, once in a tab during the test, and once as part of
OmniboxPopupPresenter regardless of the test.

Bug: 40284073, b:445424843
Change-Id: Ifde636a3bb4bb1b8ee7998cea8189ae6dab293c8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7018871
Commit-Queue: David Yeung <dayeung@chromium.org>
Auto-Submit: Demetrios Papadopoulos <dpapad@chromium.org>
Reviewed-by: David Yeung <dayeung@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1527187}