Disable the sites dropdown if only one site available

[JayBox325]

If a user's permissions only allow them to access one site, adding the dropdown here may be misleading but also needless UI.

Would be a much cleaner experience if this wasn't a dropdown if it wasn't needed.

[JayBox325]

This can also be worked when the sites dropdown is in the header:

This is a needless UX option for users if they only have access to one site.