upload: Fix flake8 E241 multiple spaces after ','

Change-Id: I3a65869f9d006027270a7826d7982950c0e6759a
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/254597
Tested-by: David Pursehouse <dpursehouse@collab.net>
Reviewed-by: Mike Frysinger <vapier@google.com>