Cleanup unused string resources

This change also renames some "completion" to "correction".

Change-Id: I156dd7ccafe99a632721f20769d5f0ea5915a564
diff --git a/java/res/xml/prefs.xml b/java/res/xml/prefs.xml
index 85612b0..1bc3395 100644
--- a/java/res/xml/prefs.xml
+++ b/java/res/xml/prefs.xml
@@ -102,13 +102,13 @@
             />
 
         <ListPreference
-            android:key="auto_completion_threshold"
-            android:title="@string/auto_complete"
-            android:summary="@string/auto_complete_summary"
+            android:key="auto_correction_threshold"
+            android:title="@string/auto_correction"
+            android:summary="@string/auto_correction_summary"
             android:persistent="true"
-            android:entryValues="@array/auto_completion_threshold_mode_values"
-            android:entries="@array/auto_completion_threshold_modes"
-            android:defaultValue="@string/auto_completion_threshold_mode_value_modest"
+            android:entryValues="@array/auto_correction_threshold_mode_values"
+            android:entries="@array/auto_correction_threshold_modes"
+            android:defaultValue="@string/auto_correction_threshold_mode_value_modest"
             />
 
         <CheckBoxPreference