Update language to comply with Android's inclusive language guidance

See https://source.android.com/setup/contribute/respectful-code for reference

Bug: 161896447
Test: robotest & manual
Change-Id: I36829e0055437dab79d9e5339ac002a87a4b874f

res/xml/privacy_settings.xml

@@ -33,7 +33,7 @@
         android:persistent="false"
         settings:controller="com.android.settings.backup.ConfigureAccountPreferenceController">
         <!-- the Intent declared here is always overwritten by a real one -->
-        <intent android:action="dummy" />
+        <intent android:action="placeholder" />
     </Preference>
 
     <Preference