VncFlinger: unset persistent attribute

Saves around ~100mb of memory in IDLE state

Change-Id: I61fe36fc7f7b6504949b69c14e62b6df32b015d3

AndroidManifest.xml

@@ -28,7 +28,6 @@
         tools:ignore="ProtectedPermissions" />
 
     <application
-        android:persistent="true"
         android:supportsRtl="true"
         android:theme="@android:style/Theme.DeviceDefault.DayNight"
         tools:ignore="MissingApplicationIcon">