Consolidate voice input key options no.1

Change-Id: I2f928522a0795f57b4133072f270d8fd2498cae9
diff --git a/java/res/xml/prefs.xml b/java/res/xml/prefs.xml
index 2a726c4..6c36b0e 100644
--- a/java/res/xml/prefs.xml
+++ b/java/res/xml/prefs.xml
@@ -42,13 +42,11 @@
             android:title="@string/popup_on_keypress"
             android:persistent="true"
             android:defaultValue="@bool/config_default_key_preview_popup" />
-        <ListPreference
-            android:key="voice_mode"
+        <CheckBoxPreference
+            android:key="pref_voice_input_key"
             android:title="@string/voice_input"
             android:persistent="true"
-            android:entryValues="@array/voice_input_modes_values"
-            android:entries="@array/voice_input_modes"
-            android:defaultValue="@string/voice_mode_main" />
+            android:defaultValue="true" />
     </PreferenceCategory>
     <PreferenceCategory
         android:title="@string/correction_category"