ANDROID: Delete build.config.gki.aarch64.16k.

This is now implemented with defconfig fragments.
define_common_kernels use the regular
build.config.gki.aarch64 and apply
16k_defconfig on it.

Bug: 286589887
Test: TH
Signed-off-by: Yifan Hong <elsk@google.com>
(cherry picked from https://android-review.googlesource.com/q/commit:03d155e488ab9e5192cb344419e219203b82ea54)
Merged-In: I71d9abd8faa19a2e517b1c9cb82f9b1a0c9b9197
Change-Id: I71d9abd8faa19a2e517b1c9cb82f9b1a0c9b9197