Few minor issue with dropdowns

[awesomerobot (Kris)]

We just merged a fix here

https://github.com/discourse/discourse/pull/14199

This covers everything except

@Don

On mobile the dropdown position not correct on few place.

https://global.discourse-cdn.com/meta/original/3X/5/e/5e5e40b39afb6456541c530dd8599b6aceb9619a.mp4

I think this has to do with popper @j.jaffeux? not sure how to approach that