Settings: Fix aria-label property in security keys credential dialog

It was populated incorrectly using "$=" instead of "=", which resulted
in the aria-label attribute missing at runtime.

Change-Id: Ie89f231ac903426a904ac74cc194478f6ae7733c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3399473
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Martin Kreichgauer <martinkr@google.com>
Auto-Submit: Martin Kreichgauer <martinkr@google.com>
Cr-Commit-Position: refs/heads/main@{#960664}