Bug 1095868 - make progress dots clickable

Bug 1095868 - Sequential form: Provide clearer way to go back to previous step
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Only preceding dots of the current active one should be clickable
Just realized I might have accidentally dropped in this line here.  It works fine if that line is removed - on both Chrome and Firefox.  But I'll see if I can clean up the code by making a function as what you suggested above.