0.6.7 Extrusion bug

[JoakimCh]

When extruding by x amount of pixels only the pixels at the edge should be repeated this many times. This is not the case, a red box with a blue outline (for example) will mix both blue and red in the extruded pixels.

This happens because ctx.imageSmoothingEnabled is true by default and needs to be set to false before doing the extrusion. This was previously fixed but sadly is broken again in 4ba6465... Undo the changes in this commit inside the renderExtrude function to fix the bug.