Fix selector collision with blame on package.json files

What does this MR do and why?

Fixes a collision in the CSS selector when viewing Blame info via the source viewer on package.json fies.

Fixes the collision by making the selector more specific.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Enable the graphql_git_blame, blob_blame_info and highlight_js_worker feature flags
2. Open a package.json file via the repository files browser
3. Click the Blame button in the blob header
4. The blame info should be rendered as expected

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #425267 (closed)