[iOS] Reset layout when activating voice over

VoiceOver scroll ability comes from a special handling of the layout
when VoiceOver is activated.
Invalidate the layout when voice over is turned on/off to make sure
the layout is correct.

Fixed: 330856099
Change-Id: I1024de47dfa5030124eef29f335d3865946e8979
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5385657


Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Auto-Submit: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Ewann Pellé <ewannpv@chromium.org>
Reviewed-by: Ewann Pellé <ewannpv@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1276830}