Fix flaky test by correcting aria typo.

Flake reported at https://chromium-review.googlesource.com/c/chromium/src/+/1108379

TBR=dtseng@chromium.org,hcarmona@chromium.org

Bug:855283

Cq-Include-Trybots: luci.chromium.try:closure_compilation
Change-Id: I16ae126ab06a8f1fdfc4c9683adc62d64e08ca72
Reviewed-on: https://chromium-review.googlesource.com/1111322Reviewed-by: Hector Carmona <hcarmona@chromium.org>
Reviewed-by: Katie Dektar <katie@chromium.org>
Commit-Queue: Katie Dektar <katie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569524}

chrome/browser/resources/settings/a11y_page/tts_subpage.html

@@ -54,7 +54,7 @@
           ticks="[[speechPitchTicks_()]]"
           min-label="$i18n{textToSpeechPitchMinimumLabel}"
           max-label="$i18n{textToSpeechPitchMaximumLabel}"
-          aria-describeby="pitch">
+          aria-describedby="pitch">
       </display-size-slider>
     </div>
     <div class="settings-box continuation">