Set default pylint version to 2.7
Set default pylint version to 2.7

This was announced in infra-announce@chromium.org.

R=bdcbd10822f2f5deecea3bf14d73e9025b1b8375@google.com

Bug: 1105747
Change-Id: I5ac21683ae8b72d7b8f1caacda5dc5faf131fd2a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3722041
Reviewed-by: Gavin Mak <bdcbd10822f2f5deecea3bf14d73e9025b1b8375@google.com>
Commit-Queue: Gavin Mak <bdcbd10822f2f5deecea3bf14d73e9025b1b8375@google.com>

CoherentLabs/depot_tools,CoherentLabs/depot_tools