Since T348286, OOUI elements like .oo-ui-windowManager and
.oo-ui-defaultOverlay are attached to the new #mw-teleport-target
element, and styles like font-size should be changed on that element,
so that they will also apply to Codex dialogs in the future.
Bug: T348287
Change-Id: I2cbd3298ed2494c68a2db1409e2975093e36d488
