d1: Remove DEXPREOPT_GENERATE_APEX_IMAGE

* Removed in https://android-review.googlesource.com/c/platform/build/+/1230120

Change-Id: I0db83d78ac34969a130975e0f730cfec9a1f55d4
diff --git a/BoardConfig.mk b/BoardConfig.mk
index ef10d30..6fc5d58 100644
--- a/BoardConfig.mk
+++ b/BoardConfig.mk
@@ -21,9 +21,6 @@
 
 DEVICE_PATH := device/samsung/d1
 
-## APEX image
-DEXPREOPT_GENERATE_APEX_IMAGE := true
-
 ## Display
 TARGET_SCREEN_DENSITY := 420