Remove dynamic summary from Security Patch info

Change-Id: I96b2e32a101077c58efd56115e70b63e4eb25049
Fixes: 36101902
Test: builds :)

res/values/strings.xml

@@ -31,8 +31,6 @@
     <string name="dlg_switch">Switch</string>
 
     <!-- Device Info --> <skip />
-    <!-- Device Info screen. Used for a status item's value when the proper value is not known -->
-    <string name="device_info_default">Unknown</string>
     <!-- [CHAR LIMIT=NONE] Device Info screen. Countdown for user taps to enable development settings -->
     <plurals name="show_dev_countdown">
         <item quantity="one">You are now <xliff:g id="step_count">%1$d</xliff:g> step away from being a developer.</item>

res/xml/device_info_settings.xml

@@ -74,7 +74,7 @@
         <!-- Security patch level -->
         <Preference android:key="security_patch"
                 android:title="@string/security_patch"
-                android:summary="@string/device_info_default">
+                android:summary="@string/summary_placeholder">
                 <intent android:action="android.intent.action.VIEW"
                         android:data="https://source.android.com/security/bulletin/" />
         </Preference>