This reverts commit 988c0af5.

Reason for revert:
This change breaks our bot: https://logs.chromium.org/logs/chromium/buildbucket/cr-buildbucket/8821937225081267713/+/u/cleanup_index.lock/stdout.

The reference for the newly added cleanup.py looks incorrect.

Original change's description:
> Update diff_deps receipe to py3
>
> Recipe-Nontrivial-Roll: build
> Bug: 1289280
> Change-Id: Ia87693ab8187acc5fa5cbd76664b999ad65d2809
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3438326
> Reviewed-by: Josip Sokcevic <sokcevic@google.com>
> Reviewed-by: Gavin Mak <gavinmak@google.com>
> Commit-Queue: Aravind Vasudevan <aravindvasudev@google.com>

Bug: 1289280
Change-Id: I8d430a29abafafe2501c73b2b20063c2a134024d
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3473364
Auto-Submit: Chidera Olibie <colibie@google.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: Aravind Vasudevan <aravindvasudev@google.com>
Commit-Queue: Aravind Vasudevan <aravindvasudev@google.com>