CrOS Settings: Audit A11y for settings-dropdown-row

Screenshot: http://screen/6GU9NBcimwsMokx.png

Bug: b:345243853
Test: browser_tests --gtest_filter="*SettingsDropdownRow*"
Change-Id: I9a200b83fb735d35c01d0a2b3617ff77f0643571
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5616174


Reviewed-by: Connie Xu <conniekxu@chromium.org>
Commit-Queue: Wes Okuhara <wesokuhara@google.com>
Cr-Commit-Position: refs/heads/main@{#1313130}