remove the iframe transport reference which no longer exists in owncloud 9.1
remove the iframe transport reference which no longer exists in owncloud 9.1

imjalpreet/gallery,imjalpreet/gallery,owncloud/gallery,interfasys/galleryplus,IATkachenko/gallery,owncloud/gallery,desaintmartin/gallery,imjalpreet/gallery,interfasys/galleryplus,IATkachenko/gallery,IATkachenko/gallery,owncloud/galleryplus,owncloud/gallery,desaintmartin/gallery,owncloud/galleryplus,owncloud/galleryplus,desaintmartin/gallery,interfasys/galleryplus