Remove hardcoded introduction bounds from hosted_legistar_scraper.py

The immediate error that @zzolo was running into was caused by https://github.com/codeforamerica/councilmatic/blob/master/councilmatic/phillyleg/management/scraper_wrappers/sources/hosted_legistar_scraper.py#L43

The scraper will not check 'ctl00$ContentPlaceHolder1$radFileCreated' unless searchLegislation is passed an 'early than' or 'later than' argument.
