fix: set private field to boolean in devtools fusebox package

[Arktomson]

Summary

This change updates packages/react-devtools-fusebox/package.json to use a boolean for the private field instead of a string.

• Changed "private": "true" to "private": true.
• This aligns the package metadata with standard package.json schema expectations.
• Scope is intentionally minimal and does not change runtime behavior.

How did you test this change?

I validated the package metadata value and type after the change.

node -e "const p=require('./packages/react-devtools-fusebox/package.json'); if (typeof p.private !== 'boolean') { throw new Error('private is not boolean'); } console.log('private is boolean:', p.private);"

Output:

private is boolean: true

Additionally, this is a metadata-only change in package.json, so no runtime code path is affected.

---