Remove, redirect retrievers examples page

[leemthompo]

• Closes https://github.com/elastic/developer-docs-team/issues/324
• Closes https://github.com/elastic/developer-docs-team/issues/325
• Depends on [DOCS] Move retrievers examples page from docs-content repo elasticsearch#131766, CI will fail until that's merged

[github-actions]

⚠️ Markdown file changes detected

The following Markdown file was removed in this PR:

• solutions/search/retrievers-examples.md

Action Required

We currently do not have an easy way to implement redirects for removed or renamed files. If possible, please:

• Keep files whenever possible and hide them from the TOC by using hidden
• Add a notice at the top of the file indicating that the page has moved with a link to the new location
• ✅ Ensure you've updated redirects.yml accordingly if files must be removed or renamed

Thank you!

[github-actions]

🔍 Preview links for changed docs

• solutions/search/retrievers-overview.md