toolbar.py: Remove '?' causing failed submission page redirects

If you went to:

http://reddit.com/someurl.com

You would get sent to:

http://www.reddit.com/submit?%3Furl=http%3A%2F%2Fsomeurl.com

Which causes the URL to not be put in the URL field; removing the ? in "/submit?" fixes this.

(resubmitted because of problems with the previous PR)