docs: simplify sidebar description

[ivancheban]

Removed at its crux because this phrase confuses the users who are not native speakers. The phrase "at its crux" means "at its core" or "at its essence." It doesn't provide the useful information for this sentence, so can be removed.

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

Test Plan

Test links

Deploy preview: https://deploy-preview-_____--docusaurus-2.netlify.app/

Related issues/PRs

[netlify]

✅ [V2]

Built without sensitive environment variables

Name	Link
🔨 Latest commit	ce09cf1
🔍 Latest deploy log	https://app.netlify.com/sites/docusaurus-2/deploys/6777afef0ed74000084f6b55
😎 Deploy Preview	https://deploy-preview-10810--docusaurus-2.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	Report
/	🔴 46	🟢 98	🟢 96	🟢 100	Report
/docs/installation	🔴 48	🟢 97	🟢 100	🟢 100	Report
/docs/category/getting-started	🟠 72	🟢 100	🟢 100	🟠 86	Report
/blog	🟠 61	🟢 96	🟢 100	🟠 86	Report
/blog/preparing-your-site-for-docusaurus-v3	🔴 46	🟢 92	🟢 100	🟢 100	Report
/blog/tags/release	🟠 64	🟢 96	🟢 100	🟠 86	Report
/blog/tags	🟠 74	🟢 100	🟢 100	🟠 86	Report

[slorber]

thanks, agree we should use simpler terms 👍