[depot_tools] Use logging.warning

logging.warn is deprecated and should be replaced with logging.warning.

Bug:1097402
Change-Id: I55ce007bec47608eeafcf3cd9ac2b90f60073115
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2575621
Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Gavin Mak <gavinmak@google.com>
diff --git a/git_cl.py b/git_cl.py
index eaba55d..5f9dba5 100755
--- a/git_cl.py
+++ b/git_cl.py
@@ -1083,11 +1083,12 @@
           remote, = remotes
         elif 'origin' in remotes:
           remote = 'origin'
-          logging.warn('Could not determine which remote this change is '
-                       'associated with, so defaulting to "%s".' % self._remote)
+          logging.warning('Could not determine which remote this change is '
+                          'associated with, so defaulting to "%s".' %
+                          self._remote)
         else:
-          logging.warn('Could not determine which remote this change is '
-                       'associated with.')
+          logging.warning('Could not determine which remote this change is '
+                          'associated with.')
         branch = 'HEAD'
       if branch.startswith('refs/remotes'):
         self._remote = (remote, branch)