Knip 7: remove unused style constants

[handeyeco]

Summary:

I could see an argument for keeping these since they define a palette we could choose from. However, we're trying to more closely align with WB so I think we should think of that as our palette rather than maintaining our own.

[khan-actions-bot]

Gerald

Required Reviewers

• @Khan/perseus for changes to knip.config.ts, package.json, yarn.lock, .changeset/proud-ligers-learn.md, packages/perseus/src/styles/constants.ts

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[github-actions]

npm Snapshot: Published

Good news!! We've packaged up the latest commit from this PR (51e0457) and published it to npm. You
can install it using the tag PR1777.

Example:

yarn add @khanacademy/perseus@PR1777

If you are working in Khan Academy's webapp, you can run:

./dev/tools/bump_perseus_version.sh -t PR1777

[github-actions]

Size Change: -448 B (-0.05%)

Total Size: 867 kB

Filename	Size	Change
packages/perseus/dist/es/index.js	419 kB	-448 B (-0.11%)

ℹ️ View Unchanged

Filename	Size
packages/kas/dist/es/index.js	38.8 kB
packages/keypad-context/dist/es/index.js	760 B
packages/kmath/dist/es/index.js	4.27 kB
packages/math-input/dist/es/index.js	78 kB
packages/math-input/dist/es/strings.js	1.79 kB
packages/perseus-core/dist/es/index.js	1.48 kB
packages/perseus-editor/dist/es/index.js	281 kB
packages/perseus-linter/dist/es/index.js	22.2 kB
packages/perseus/dist/es/strings.js	3.4 kB
packages/pure-markdown/dist/es/index.js	3.66 kB
packages/simple-markdown/dist/es/index.js	12.4 kB

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[benchristel]

LGTM.