Remove apex_debug_key

Remove apex_debug_key, in favor of apex.test.key which is under
/system/apex and is built with soong.

Bug: 118213152
Test: /system/etc/security/apex/testkey exists
Change-Id: Iaa0facea2d26cadd48783778e8915bc3c560de10
diff --git a/target/product/base_system.mk b/target/product/base_system.mk
index 91071fd..7b70c86 100644
--- a/target/product/base_system.mk
+++ b/target/product/base_system.mk
@@ -309,7 +309,7 @@
 # Packages included only for eng or userdebug builds, previously debug tagged
 PRODUCT_PACKAGES_DEBUG := \
     adb_keys \
-    apex_debug_key \
+    apex.test.key \
     iotop \
     logpersist.start \
     perfprofd \