Remove the color tokens from the legacy theme

[connor-baer]

Purpose

We introduced semantic color tokens as CSS variables in Circuit UI v6.1. Developers have had plenty of time to migrate their code, so it's time to remove the legacy color tokens.

Approach and changes

• Removed the color tokens from the legacy JavaScript theme object.
• Disabled the theme switcher in Storybook. It will be re-enabled once there is a dark theme.

Definition of done

• Development completed
• Reviewers assigned
• Unit and integration tests
• Meets minimum browser support
• Meets accessibility requirements

[changeset-bot]

🦋 Changeset detected

Latest commit: f43b9ce

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

Name	Type
@sumup/design-tokens	Major
@sumup/astro-template-circuit-ui	Patch
@sumup/circuit-ui	Major
@sumup/eslint-plugin-circuit-ui	Major
@sumup/remix-template-circuit-ui	Patch
@sumup/stylelint-plugin-circuit-ui	Major

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Name	Status	Preview	Comments	Updated (UTC)
oss-circuit-ui	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Dec 21, 2023 4:06pm

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (f33c269) 96.81% compared to head (f43b9ce) 96.78%.

Additional details and impacted files

@@            Coverage Diff             @@
##           canary    #2355      +/-   ##
==========================================
- Coverage   96.81%   96.78%   -0.04%     
==========================================
  Files         228      227       -1     
  Lines       19016    18833     -183     
  Branches     1172     1173       +1     
==========================================
- Hits        18410    18227     -183     
  Misses        593      593              
  Partials       13       13              

Files	Coverage Δ
packages/design-tokens/scripts/build.ts	96.58% <100.00%> (+0.50%)	⬆️
packages/design-tokens/themes/legacy/light.ts	100.00% <100.00%> (ø)
packages/design-tokens/utils/theme-prop-type.ts	100.00% <100.00%> (ø)