avicii: Disable debug.sf.latch_unsignaled from prop.

* Disabling this helps reduces notification flicker, UI performance is not impacted.
(per:  change https://android.googlesource.com/platform/frameworks/native/+/c5da271)

system_ext.prop

@@ -9,7 +9,7 @@ persist.bluetooth.bqr.min_interval_ms=60000
 
 # Display
 debug.sf.enable_hwc_vds=1
-debug.sf.latch_unsignaled=1
+debug.sf.latch_unsignaled=0
 
 # CNE
 persist.vendor.cne.feature=1