Fix the code link urls throughout the project

[jimmynotjim]

The code link url was outdated and pointing to the wrong file. Updated it to point to the correct file as well as removing duplications.

Removals

• Duplicate code link headings

Changes

• Fixed the code link url

Review

• @Scotchester
• @nataliafitzgerald

Preview this PR without the whitespace changes

Checklist

• [ ] Changes are limited to a single goal (no scope creep)
• [ ] Code can be automatically merged (no conflicts)
• [ ] Code follows the standards laid out in the front end playbook
• [ ] Passes all existing automated tests
• [ ] New functions include new tests
• [ ] New functions are documented (with a description, list of inputs, and expected output)
• [ ] Placeholder code is flagged
• [ ] Visually tested in supported browsers and devices
• [ ] Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)

[jimmynotjim]

@Scotchester Updated all the links to source code I could find.

[jimmynotjim]

@Scotchester RE: tree vs blob I didn't know how best to link to code when a component covers it all, such as cf-expandables, vs something like heros which are a very small part of cf-layout. If we're going to settle on one, I'd prefer components (aka tree), but I'm open to suggestions.

[Scotchester]

Ohhhh... I'm dumb. Didn't even dawn on me that tree vs. blob is directory vs. file.

Forget that comment, I agree with your logic.

[Scotchester]

🚢