removed duplicated entry from the README.rst
removed duplicated entry from the README.rst

See #1189

tsiegleauq/OpenSlides,emanuelschuetze/OpenSlides,normanjaeckel/OpenSlides,emanuelschuetze/OpenSlides,ostcar/OpenSlides,FinnStutzenstein/OpenSlides,boehlke/OpenSlides,FinnStutzenstein/OpenSlides,tsiegleauq/OpenSlides,normanjaeckel/OpenSlides,jwinzer/OpenSlides,rolandgeider/OpenSlides,CatoTH/OpenSlides,normanjaeckel/OpenSlides,jwinzer/OpenSlides,boehlke/OpenSlides,ostcar/OpenSlides,rolandgeider/OpenSlides,jwinzer/OpenSlides,CatoTH/OpenSlides,FinnStutzenstein/OpenSlides,emanuelschuetze/OpenSlides,boehlke/OpenSlides,tsiegleauq/OpenSlides,CatoTH/OpenSlides,OpenSlides/OpenSlides,CatoTH/OpenSlides,ostcar/OpenSlides,OpenSlides/OpenSlides,boehlke/OpenSlides,jwinzer/OpenSlides,FinnStutzenstein/OpenSlides,jwinzer/OpenSlides,rolandgeider/OpenSlides,normanjaeckel/OpenSlides,emanuelschuetze/OpenSlides