Color: Renaming variables is broken

[lanzagar]

Describe the bug
After renaming a variable in the Color widget all its values are unknown/missing (?).

Orange version:
3.25

[ajdapretnar]

I don't think Color should enable renaming variables. I mean... why? We have Edit Domain for that.

[janezd]

It's sometimes practical - we can also change a color for a certain value and rename it.

It is also quite nicely implemented, integrated into models, tested... Removing this functionality would require rewriting the widget (or keeping a lot of unused stuff in it). Fixing this issue is trivial - it was just a missing argument. #4669 is ready for review.