Remove long-deprecated khan-exercise.css

[jeremywiebe]

Summary:

Today's the day - rm khan-exercise.css.

The khan-exercise.css stylesheet is a very old set of styles for Perseus. Many of the styles apply to elements that live in webapp and not in Perseus so they don't even belong here. Some are unscoped and so also are just bad practices. Lastly, webapp applies a CSS Reset at the start of it's styles so I suspect most of the unscoped rules are clobbered anyways.

The remaining rules will either exist in webapp/mobile already or be for elements that no longer exist.

This file just confuses things so I'm removing it today!

Issue: --none--

Test plan:

[github-actions]

Size Change: 0 B

Total Size: 832 kB

ℹ️ View Unchanged

Filename	Size
packages/kas/dist/es/index.js	38.1 kB
packages/kmath/dist/es/index.js	4.25 kB
packages/math-input/dist/es/index.js	79 kB
packages/perseus-core/dist/es/index.js	908 B
packages/perseus-editor/dist/es/index.js	270 kB
packages/perseus-error/dist/es/index.js	877 B
packages/perseus-linter/dist/es/index.js	21.8 kB
packages/perseus/dist/es/index.js	402 kB
packages/pure-markdown/dist/es/index.js	3.77 kB
packages/simple-markdown/dist/es/index.js	12.4 kB

_{compressed-size-action}

[khan-actions-bot]

Gerald

Required Reviewers

• @Khan/perseus for changes to .changeset/lovely-seahorses-hide.md, packages/perseus/src/styles/perseus-renderer.less

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[codecov]

Codecov Report

Merging #875 (044e74c) into main (20db666) will increase coverage by 1.31%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #875      +/-   ##
==========================================
+ Coverage   62.24%   63.56%   +1.31%     
==========================================
  Files         406      408       +2     
  Lines       99371    99388      +17     
  Branches     6206     8670    +2464     
==========================================
+ Hits        61851    63172    +1321     
+ Misses      37520    36216    -1304     

see 31 files with indirect coverage changes

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[github-actions]

npm Snapshot: Published

🎉 Good news!! We've packaged up the latest commit from this PR (044e74c) and published it to npm. You
can install it using the tag PR875.

Example:

yarn add @khanacademy/perseus@PR875

[handeyeco]

This is great 🎉 Makes me a little nervous with the upcoming mobile app release though.

• Should we wait to land this until after the release?
• Do we need a full QE Perseus pass to check for issues?