Project download buttons always show
## What does this MR do?
Removes `hidden-xs hidden-sm` classes from `download-button` so it doesn’t hide itself individually from the rest of the `project-repo-buttons` block
## Why was this MR needed?
Fixes#23960. Not sure why this element had these classes in the first place, but at the very least we shouldn’t be hiding the Download button at the `hidden-sm` threshold since that’s still fairly large viewport and users with viewports of that size likely still want to download source code.
## Screenshots (if relevant)
Screenshots taken at ~830px width
__Before__
__After__
## What are the relevant issue numbers?
#23960
See merge request !7405
7f151a7898