Set the layout of seekbar as the preference_iconless_slider

and remove the higher speech rate preference variables.
The layout is changed to preference_iconless_slider so that the speech
rate slider layout is same as the layout of seekbars in android
settings.

Bug: 27136737
Change-Id: Ib75b8dec74ef07be87130a3f29249b148f4bcf0b

src/com/android/settings/tts/TextToSpeechSettings.java

@@ -89,18 +89,12 @@ public class TextToSpeechSettings extends SettingsPreferenceFragment implements
 
     private PreferenceCategory mEnginePreferenceCategory;
     private SeekBarPreference mDefaultRatePref;
-    private SwitchPreference mHigherRateSwitchPref;
     private Preference mResetSpeechRate;
     private Preference mPlayExample;
     private Preference mEngineStatus;
 
     private int mDefaultRate = TextToSpeech.Engine.DEFAULT_RATE;
 
-    /**
-     * Whether higher speech rate is enabled.
-     */
-    private boolean mHigherRateSwitch = false;
-
     /**
      * The currently selected engine.
      */