yapf: remove unused `re` import

Bug: None
Change-Id: I4c161b05ab5c743cf8d6fddbf40af759f186eccc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3782487Reviewed-by: Gavin Mak <gavinmak@google.com>
Reviewed-by: Aravind Vasudevan <aravindvasudev@google.com>
Commit-Queue: Thiago Perrotta <tperrotta@chromium.org>
Auto-Submit: Thiago Perrotta <tperrotta@chromium.org>

yapf

@@ -12,7 +12,6 @@
 # [VPYTHON:END]
 
 # -*- coding: utf-8 -*-
-import re
 import sys
 
 from yapf import run_main