Remove no-op config.

This was copied over from when Soong required us to define it in the
properties file, but this is the default and we also don't care.

Bug: None
Test: None
Change-Id: I35311093c83fddcb7c413535fbb50a126b615036
diff --git a/target/board/ndk/BoardConfig.mk b/target/board/ndk/BoardConfig.mk
index d5399b2..c7d9d4c 100644
--- a/target/board/ndk/BoardConfig.mk
+++ b/target/board/ndk/BoardConfig.mk
@@ -16,5 +16,3 @@
 TARGET_ARCH_SUITE := ndk
 
 MALLOC_LOW_MEMORY := true
-
-USE_SAFESTACK := false