You can’t. It’s not possible in Gravity Forms 2.3. The third parameter to get_entries() is not designed to accept more than one sort field. Use array_multisort() instead.

		$entries = GFAPI::get_entries( 22, '', null ); //form #22 Food vendor app

		$sort = array();
		foreach( $entries as $k => $v ) {
		    $sort['is_approved'][$k] = $v['is_approved'];
		    $sort['16'][$k] = $v['16']; //field #16 Company name
		}
		array_multisort( $sort['is_approved'], SORT_DESC, $sort['16'], SORT_ASC, $entries );