[git-cl] Remove apparently effect-less import

Change-Id: Ief9948f5331945359696de8e158af021a6ade7ca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1709804
Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Quinten Yearsley <qyearsley@chromium.org>

git_cl.py

@@ -37,11 +37,6 @@ import uuid
 import webbrowser
 import zlib
 
-try:
-  import readline  # pylint: disable=import-error,W0611
-except ImportError:
-  pass
-
 from third_party import colorama
 from third_party import httplib2
 import auth