Set default pylint version to 2.7

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

R=gavinmak@google.com

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

presubmit_canned_checks.py

@@ -1003,7 +1003,7 @@ def GetPylint(input_api,
               disabled_warnings=None,
               extra_paths_list=None,
               pylintrc=None,
-              version='1.5'):
+              version='2.7'):
   """Run pylint on python files.
 
   The default files_to_check enforces looking only at *.py files.