[accessibility] Update slider labels to consistent min/max labeling

- Some settings pages use min adjective/max adjective while others use
  min superlative/max superlative, this CL updates a page that used
  min superlative/max superlative to use min adjective/max, as most
  sliders currently use min adjective/max. I went through all pages and
  confirmed that only text to speach uses superlative/max superlative.
- Confirmed with UI (mikinm@).

screenshot: https://screenshot.googleplex.com/8VSH24Jfc3W8TUH.png

Bug: 1032258
Change-Id: Icf574864093f999b81ee2d0e7ed4bbd61617dd22
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2458446Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: Nnamdi Theodore Johnson-kanu <tjohnsonkanu@google.com>
Cr-Commit-Position: refs/heads/master@{#814895}

chrome/app/os_settings_strings.grdp

@@ -1019,28 +1019,28 @@
     Rate
   </message>
   <message name="IDS_SETTINGS_TEXT_TO_SPEECH_RATE_MINIMUM_LABEL" desc="A label for the minimum side of a slider allowing users to change their text-to-speech speech rate">
-    Slowest
+    Slow
   </message>
   <message name="IDS_SETTINGS_TEXT_TO_SPEECH_RATE_MAXIMUM_LABEL" desc="A label for the maximum side of a slider allowing users to change their text-to-speech speech rate">
-    Fastest
+    Fast
   </message>
   <message name="IDS_SETTINGS_TEXT_TO_SPEECH_PITCH" desc="The pitch of speech in text-to-speech settings.">
     Pitch
   </message>
   <message name="IDS_SETTINGS_TEXT_TO_SPEECH_PITCH_MINIMUM_LABEL" desc="A label for the minimum side of a slider allowing users to change their text-to-speech speech pitch">
-    Lowest
+    Low
   </message>
   <message name="IDS_SETTINGS_TEXT_TO_SPEECH_PITCH_MAXIMUM_LABEL" desc="A label for the maximum side of a slider allowing users to change their text-to-speech speech pitch">
-    Highest
+    High
   </message>
   <message name="IDS_SETTINGS_TEXT_TO_SPEECH_VOLUME" desc="The volume of speech compared to system volume in text-to-speech settings.">
     Volume
   </message>
   <message name="IDS_SETTINGS_TEXT_TO_SPEECH_VOLUME_MINIMUM_LABEL" desc="A label for the minimum side of a slider allowing users to change their text-to-speech speech volume">
-    Quietest
+    Quiet
   </message>
   <message name="IDS_SETTINGS_TEXT_TO_SPEECH_VOLUME_MAXIMUM_LABEL" desc="A label for the maximum side of a slider allowing users to change their text-to-speech speech volume">
-    Loudest
+    Loud
   </message>
   <message name="IDS_SETTINGS_PERCENTAGE" desc="A number displayed as a percentage">
     <ph name="PERCENTAGE">$1<ex>120</ex></ph>%

chrome/app/os_settings_strings_grdp/IDS_SETTINGS_TEXT_TO_SPEECH_PITCH_MAXIMUM_LABEL.png.sha1

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chrome/app/os_settings_strings_grdp/IDS_SETTINGS_TEXT_TO_SPEECH_PITCH_MINIMUM_LABEL.png.sha1

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chrome/app/os_settings_strings_grdp/IDS_SETTINGS_TEXT_TO_SPEECH_RATE_MAXIMUM_LABEL.png.sha1

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chrome/app/os_settings_strings_grdp/IDS_SETTINGS_TEXT_TO_SPEECH_RATE_MINIMUM_LABEL.png.sha1

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chrome/app/os_settings_strings_grdp/IDS_SETTINGS_TEXT_TO_SPEECH_VOLUME_MAXIMUM_LABEL.png.sha1

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chrome/app/os_settings_strings_grdp/IDS_SETTINGS_TEXT_TO_SPEECH_VOLUME_MINIMUM_LABEL.png.sha1

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