Remove fast-colors package (#6969)

# Pull Request

## 📖 Description

Removal of the `@microsoft/fast-colors` package.

### 🎫 Issues

Resolves #6950.

## 👩‍💻 Reviewer Notes

Discussions have been had with original maintainers and removal of this package is not an issue.

## ✅ Checklist

### General

<!--- Review the list and put an x in the boxes that apply. -->

- [ ] I have included a change request file using `$ yarn change`
- [ ] I have added tests for my changes.
- [x] I have tested my changes.
- [x] I have updated the project documentation to reflect my changes.
- [x] I have read the [CONTRIBUTING](https://github.com/microsoft/fast/blob/master/CONTRIBUTING.md) documentation and followed the [standards](/docs/community/code-of-conduct/#our-standards) for this project.

Author: janechu

.github/CODEOWNERS

@@ -33,7 +33,6 @@ build/ @janechu @nicholasrice @chrisdholt @awentzel
 
 # Utilities
 /packages/utilities/fast-animation/ @nicholasrice @chrisdholt
-/packages/utilities/fast-colors/ @nicholasrice @chrisdholt
 /packages/utilities/fast-eslint-rules/ @nicholasrice @janechu @chrisdholt
 /packages/utilities/fast-web-utilities/ @janechu @chrisdholt @nicholasrice