Fixing ChromeVox languageSwitchingOption typo introduced in crrev.com/f08ad04

R=dtseng,aboxhall

Change-Id: Ia01ff50bc0df963df1fba50001cfa5138ef8486a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1564356
Reviewed-by: Alice Boxhall <aboxhall@chromium.org>
Commit-Queue: Alice Boxhall <aboxhall@chromium.org>
Commit-Queue: Chris Hall <chrishall@chromium.org>
Auto-Submit: Chris Hall <chrishall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#650199}