docs: fix default value for docRootComponent

[ultimate]

Hi,

this is my first PR for docusaurus - although just some documentation fix, please let me know if something is missing.

Pre-flight checklist

• I have read the Contributing Guidelines on pull requests.
• If this is a code change: I have written unit tests and/or added dogfooding pages to fully verify the new behavior.
• If this is a new API or substantial change: the PR has an accompanying issue (closes #0000) and the maintainers have approved on my working plan.

Motivation

Fix #10336

Test Plan

I ran docusaurus start and checked the changes in the documentation visually.

Deploy preview: https://deploy-preview-10337--docusaurus-2.netlify.app/docs/api/plugins/@docusaurus/plugin-content-docs#docRootComponent

[netlify]

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[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	Report
/	🟠 82	🟢 98	🟢 96	🟢 100	Report
/docs/installation	🟠 55	🟢 97	🟢 100	🟢 100	Report
/docs/category/getting-started	🟠 75	🟢 100	🟢 100	🟠 86	Report
/blog	🟠 69	🟢 96	🟢 100	🟠 86	Report
/blog/preparing-your-site-for-docusaurus-v3	🟠 53	🟢 92	🟢 100	🟢 100	Report
/blog/tags/release	🟠 70	🟢 96	🟢 100	🟠 86	Report
/blog/tags	🟠 75	🟢 100	🟢 100	🟠 86	Report

[OzakIOne]

I've added the deploy preview and modified title and text of the PR, LGTM

[slorber]

thanks 👍