Bug 1886114 - Remove fail-if notation from the Firefox View test passing a11y-checks. r=sfoster,fxview-reviewers

the updated version of the Show More link activation has resolved the issue that was there before: the link used to be clicked when it still had `hidden` attribute on - probably, right before it was rendered as shown/un-hidden, since the test harness is moving too fast. In this updated case, all the instances of the Show More links being clicked while they are visible and, therefore, accessible for the Accessibility API. We could safely remove the `fail-if` since it's working now as expected

Differential Revision: https://phabricator.services.mozilla.com/D205151

browser/components/firefoxview/tests/browser/browser.toml

@@ -51,7 +51,6 @@ skip-if = ["true"] # Bug 1851453
 ["browser_opentabs_firefoxview.js"]
 
 ["browser_opentabs_more.js"]
-fail-if = ["a11y_checks"] # Bugs 1858041, 1854625, and 1872174 clicked Show all link is not accessible because it is "hidden" when clicked
 skip-if = ["verify"] # Bug 1886017
 
 ["browser_opentabs_pinned_tabs.js"]