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

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

Change-Id: If4ceeba275a5e16493d40f226021f8fe3aa7fe21