Followup fix for https://crrev.com/c/2587268

https://crrev.com/c/2587268 changed function signatures to remove a
project argument. One function call was missed in the CL. This CL fixes
the function call.

Change-Id: Ice45072aa467ed6c56efabf405a7aac03f4b047c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2613785
Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Stephen Martinis <martiniss@chromium.org>

git_cl.py

@@ -1384,7 +1384,7 @@ class Changelist(object):
             f for f in files
             if status[f] == owners_client.INSUFFICIENT_REVIEWERS
         ]
-        add_owners = client.SuggestOwners(project, branch, missing_files)
+        add_owners = client.SuggestOwners(missing_files)
       change_description.update_reviewers(
           options.reviewers, options.tbrs, options.add_owners_to, add_owners)