Remove lingering patched-yasm directory.

Seems the DEPS checkout was hiding a directory still checked into the
main source tree.

TBR=davidben

Fixed: 766721
Change-Id: I96d3fc54d6960716cb97d36f66c61d8e5c964313
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2165573
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Reviewed-by: David Benjamin <davidben@chromium.org>
Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#762457}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 3675dde32d8d128bae9bb911ca00d8f3858816ed