sample-primitive example don't show points grid

[jorgeluismireles]

In Ubuntu sample-primitives compilation don't show the points at the lower left quadrant.

static void draw_points(void)

[edubart]

I confirm that this started happening for me on GL/GLES backends, but not on D3D11, will investigate eventually. I suspect is due to recent changes in Sokol GFX.

[edubart]

Fixed this in adbe393