[third_party][openthread] Remove extra folder

Removed third_party/openthread/openthread-tmp
as soft-transition is done now.

Bug: 66867
Tests: No real change, deleted extra folder
Change-Id: I2ed0d2926ebacc4b1a2bf160eebc1c46c097c636
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/openthread/+/465421
Reviewed-by: Parag Dixit <paragdixit@google.com>
2600 files changed