Remove external/ukey2/.gitmodules and submodule directories. am: e711039fa9 am: 492edd667d am: fbfc8c2de3 am: b17f755513 am: a497b2f9fa

Original change: https://android-review.googlesource.com/c/platform/external/ukey2/+/1830387

Change-Id: I18e2cd03ebd25f0df309fa7a425f16a7c92c2a1e