This is a reland of 2d29261e

Original change's description:
> Remove exception for relative CIPD
> 
> This seems to no longer be necessary, as relative paths 'just work' for
> CIPD deps now.
> 
> Change-Id: I3843548dc74d29af90e0c402f0459dbe60934423
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1529132
> Reviewed-by: Dirk Pranke <dpranke@chromium.org>
> Reviewed-by: John Budorick <jbudorick@chromium.org>
> Commit-Queue: Brandon Tolsch <btolsch@chromium.org>

Change-Id: Idac857ead961587e7295c9be6d53c578448eb6b2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1532268Reviewed-by: John Budorick <jbudorick@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Brandon Tolsch <btolsch@chromium.org>