Drop half circles from arc style?

While waiting for my mise downloads to finish I noticed that the spinner's implied motion appeared choppy because the arcs transition at only two of the steps.

Since Unicode has no left or right half circle character, would you consider removing "◠" and "◡" from the [arc spinner steps](https://github.com/jdx/clx/blob/48fcfb559922ff586571d23e8bcfb8e8c9e1a621/src/progress/spinners.rs#L55) so that the animation becomes more consistent?