fix summary of theme preference

Author: jbb01

app/src/main/res/values-de/strings.xml

@@ -422,7 +422,6 @@
 
     <string name="preferences_general_group_appearance">Darstellung</string>
     <string name="preferences_general_theme_title">Farbschema</string>
-    <string name="preferences_general_theme_summary">Foo Bar</string>
 
     <string name="preferences_general_group_update_check">Updates</string>
     <string name="preferences_general_update_check_enabled_title">Auf Updates prüfen</string>

app/src/main/res/values/strings.xml

@@ -488,7 +488,6 @@
 
     <string name="preferences_general_group_appearance">Appearance</string>
     <string name="preferences_general_theme_title">Theme</string>
-    <string name="preferences_general_theme_summary">Foo Bar</string>
 
     <string name="preferences_general_group_update_check">Update Check</string>
     <string name="preferences_general_update_check_enabled_title">Check for Updates</string>

app/src/main/res/xml/preferences_general.xml

@@ -31,11 +31,11 @@
         <ListPreference
             android:key="@string/preferences_general_theme_key"
             android:title="@string/preferences_general_theme_title"
-            android:summary="@string/preferences_general_theme_summary"
             android:icon="@drawable/ic_settings_theme"
             android:entries="@array/theme_names"
             android:entryValues="@array/theme_codes"
-            android:defaultValue="LIGHT"/>
+            android:defaultValue="LIGHT"
+            app:useSimpleSummaryProvider="true"/>
     </PreferenceCategory>
 
     <PreferenceCategory