Dropdown: Deprecate dropDirection prop

[silvalaura]

Now that we've implemented Floating UI, we don't have a need for the dropDirection prop for Dropdown. We can't completely remove it because our adopters expect it, so we need to deprecate it and explain in our docs that they will not need this in the future. We need to explain that in the future, the arrow will always be down, and the dropdown will open automatically wherever there is room on the screen.

[silvalaura]

@orion-cengage to add more details to ticket as needed

[chris-cedrone-cengage]

Deprecate dropDirection and alignment props and update documentation. ✅

Verified on:

https://next--upbeat-sinoussi-f675aa.netlify.app/api/dropdown/