Remove obsolete assets from target /system/media/video/

These were previously used for background replacement effect, but it seems
like they aren't needed any more and just take up space in filesystem.

Change-Id: I0782ac0c8f109e4f28e9f43c20d30dc6ccd82ef7
diff --git a/CleanSpec.mk b/CleanSpec.mk
index 8809bc7..797d088 100644
--- a/CleanSpec.mk
+++ b/CleanSpec.mk
@@ -179,6 +179,7 @@
 $(call add-clean-step, rm -rf $(PRODUCT_OUT)/system/usr/idc/frameworks)
 $(call add-clean-step, rm -rf $(PRODUCT_OUT)/system/usr/keylayout/frameworks)
 $(call add-clean-step, rm -rf $(PRODUCT_OUT)/system/usr/keychars/frameworks)
+$(call add-clean-step, rm -f $(PRODUCT_OUT)/system/media/video/*)
 # ************************************************
 # NEWER CLEAN STEPS MUST BE AT THE END OF THE LIST
 # ************************************************