fix(build): add prettier to devDependencies

[b0o]

Issue for this PR

Fixes #23256

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Fixes build error caused by #23228, which added a prettier step to generate.ts which broke Nix builds due to missing dev dependency.

How did you verify your code works?

Build succeeds

Screenshots / recordings

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

[github-actions]

Thanks for updating your PR! It now meets our contributing guidelines. 👍

[jerome-benoit]

The PR needs a bun install to regenerate the lockfile after adding prettier to package.json, otherwise the Nix node_modules hash will still be stale.

[b0o]

@jerome-benoit oops, should be fixed