Do not the mark main alerts/notifications area as aria-hidden.
Focusable descendents within an [aria-hidden="true"] element prevent those interactive elements from being available to users of assistive technologies like screen readers.
As can be seen in the code of `PhabricatorMainMenuView`, all three icons already define some `$aural[]` array to include output for assistive technologies, so their parent element should not block accessing that output.
See T16072