cursor on static sliders should not show resize

[archmoj]

    Note @archmoj: it seems to work, but a small last thing: the mouse cursor on hover of the sliders still change to `ew-resize` , ie "movable" cursor, and it should not if staticPlot = true. Maybe for 2.16.5.2 ;)

Originally posted by @josephernest in #6393 (comment)