Code cleanup: removed old vertex shader
Code cleanup: removed old vertex shader

michaelaye/vispy,drufat/vispy,michaelaye/vispy,ghisvail/vispy,Eric89GXL/vispy,Eric89GXL/vispy,drufat/vispy,Eric89GXL/vispy,ghisvail/vispy,michaelaye/vispy,drufat/vispy,ghisvail/vispy