Remove external/ms-tpm-20-ref/.gitmodules and submodule directories am: 5d68d01a1a am: fac045177b am: ef87020c15

Original change: https://android-review.googlesource.com/c/platform/external/ms-tpm-20-ref/+/1830606

Change-Id: If48fad75eb49e986d837025a8624467c3894efde