app-controls: Make feature toggle only vocalize the title

The toggle was vocalizing the menu item title and the learn more link
that is nested in the title div. Using aria-label instead of
aria-labelledby addresses the problem.

Tested: locally on device

Bug: b:345515514
Change-Id: Id4b2e76084fc7374dcaaa5eb3e06c1168cddd98d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5605550


Reviewed-by: Courtney Wong <courtneywong@chromium.org>
Commit-Queue: Aga Wronska <agawronska@chromium.org>
Auto-Submit: Aga Wronska <agawronska@chromium.org>
Reviewed-by: Wes Okuhara <wesokuhara@google.com>
Cr-Commit-Position: refs/heads/main@{#1312194}