UI: Fix button contrast-ratio

[maheshchandra10]

Closes #23454

What I did

The contrast ratio of the RAW button was not >= 4.5, so I changed the color of the button to achieve this. I have used a darker color from the existing colors which are used in the application.

Checklist for Contributors

Testing

The changes in this PR are covered in the following automated tests:

• stories
• unit tests
• integration tests
• end-to-end tests

Manual testing

1. Run the application using yarn start
2. Open Storybook in your browser
3. Navigate to the app bar present in the left pane using tab key and invoke it using Enter key.
4. In Search Components search-bar, search for 'inline', and select Padded Inline.
5. Now navigate to “Controls” tab. There you can see RAW button. Check the contrast ratio of this button. It should be greater than equal to 4.5. With my change, the contrast ratio is now 5.72

Documentation

• Add or update documentation reflecting your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Checklist for Maintainers

• When this PR is ready for testing, make sure to add ci:normal, ci:merged or ci:daily GH label to it to run a specific set of sandboxes. The particular set of sandboxes can be found in code/lib/cli/src/sandbox-templates.ts

• Make sure this PR contains one of the labels below:

  Available labels

  • bug: Internal changes that fixes incorrect behavior.
  • maintenance: User-facing maintenance tasks.
  • dependencies: Upgrading (sometimes downgrading) dependencies.
  • build: Internal-facing build tooling & test updates. Will not show up in release changelog.
  • cleanup: Minor cleanup style change. Will not show up in release changelog.
  • documentation: Documentation only changes. Will not show up in release changelog.
  • feature request: Introducing a new feature.
  • BREAKING CHANGE: Changes that break compatibility in some way with current major version.
  • other: Changes that don't fit in the above categories.

🦋 Canary release

This PR does not have a canary release associated. You can request a canary release of this pull request by mentioning the @storybookjs/core team here.

core team members can create a canary release here or locally with gh workflow run --repo storybookjs/storybook canary-release-pr.yml --field pr=<PR_NUMBER>

[cdedreuille]

Thanks @maheshchandra10 for this change. This looks great. We are making quite a lot of cosmetic changes on the sidebar for Storybook 8.0. I'll make sure this fix is there as well.