instance_drawing.cpp improvements

[kybr]

I'm talking about this example:

examples/graphics/instance_drawing.cpp

Float4 is just a Vec4f, so use a Vec4f. Except the fourth element is always 1, so use Vec3f instead, unless this operation is much more efficent than vec4 p = vec4(scale * position + offset, 1.0); where offset is a vec3.

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[younkhg]

Using Float4 was to show that any user data struct can be used. I'll add comment about it. Changing to vec3 seems correct.

pushed f654d2202f8fed8ed225fe135e3d1e94da111613

[mantaraya36]

I believe the issue has been solved by f654d22