[WebAuthn] Use correct string for confirm button

This one is already translated.

Bug: 40274370
Change-Id: I4ec881c4830e9d24628f3758cd204266d0f814ec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5355863


Reviewed-by: Adam Langley <agl@chromium.org>
Commit-Queue: Adam Langley <agl@chromium.org>
Auto-Submit: Rafał Godlewski <rgod@google.com>
Cr-Commit-Position: refs/heads/main@{#1270615}