Settings TypeScript: Add definitions for chrome.passwordsPrivate.

Bug: 1234307
Change-Id: I1dfd83476fccec726dacd519aba1743290f82279
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3141015


Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Auto-Submit: dpapad <dpapad@chromium.org>
Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Cr-Commit-Position: refs/heads/main@{#918332}