This reverts commit b576ab3b78.
Reason for revert: http://b/389876151
Original change's description:
> add support for -U in presubmit_diff.py
>
> presubmit_diff.py is going to be used to compute the changes to be
> formatted, and -U helps minimize the number of irrelevant lines
> from formatting.
>
> Bug: 379902295
> Change-Id: I9c0a2ee6b5ffa6b9fe4427362556020d525f1105
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/6168707
> Reviewed-by: Gavin Mak <gavinmak@google.com>
> Commit-Queue: Scott Lee <ddoman@chromium.org>
Bug: 379902295
Change-Id: I82dd707e5ae3d4b1760e632506ee0e1bc1d76e09
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/6173760
Reviewed-by: Scott Lee <ddoman@chromium.org>
Commit-Queue: Gavin Mak <gavinmak@google.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
