fix line_update example
fix line_update example

sbtlaarzc/vispy,drufat/vispy,inclement/vispy,RebeccaWPerry/vispy,michaelaye/vispy,QuLogic/vispy,dchilds7/Deysha-Star-Formation,ghisvail/vispy,sh4wn/vispy,michaelaye/vispy,ghisvail/vispy,julienr/vispy,dchilds7/Deysha-Star-Formation,inclement/vispy,jdreaver/vispy,RebeccaWPerry/vispy,Eric89GXL/vispy,drufat/vispy,julienr/vispy,julienr/vispy,Eric89GXL/vispy,srinathv/vispy,bollu/vispy,kkuunnddaannkk/vispy,srinathv/vispy,QuLogic/vispy,jdreaver/vispy,RebeccaWPerry/vispy,bollu/vispy,kkuunnddaannkk/vispy,sbtlaarzc/vispy,QuLogic/vispy,Eric89GXL/vispy,dchilds7/Deysha-Star-Formation,sh4wn/vispy,inclement/vispy,sh4wn/vispy,michaelaye/vispy,drufat/vispy,kkuunnddaannkk/vispy,srinathv/vispy,sbtlaarzc/vispy,jay3sh/vispy,jay3sh/vispy,jdreaver/vispy,bollu/vispy,ghisvail/vispy,jay3sh/vispy