elementadded: Use gst_value_deserialize to read properties
elementadded: Use gst_value_deserialize to read properties

Use the existing function instead of having our own less-capable re-implementation

ahmedammar/skype_farsight2,tieto/farstream,pexip/farstream,shadeslayer/farstream,pexip/farstream,pexip/farstream,tieto/farstream,shadeslayer/farstream,tieto/farstream,ahmedammar/skype_farsight2,kakaroto/farstream,ahmedammar/skype_farsight2,kakaroto/farstream,shadeslayer/farstream,tieto/farstream,shadeslayer/farstream,kakaroto/farstream,kakaroto/farstream,tieto/farstream,ahmedammar/skype_farsight2,pexip/farstream