Fix: Broken links in related_resources.md and README.md

[iamarunbrahma]

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Summary

This PR fixes broken documentation links in related_resources.md and examples/vector_databases/README.md. The changes ensure all external documentation links are up-to-date and functional, improving the cookbook's reliability and user experience.

Motivation

Several documentation links in our repository were outdated or broken due to external documentation restructuring by various providers. These changes were necessary to:

1. Ensure users can access the correct documentation resources
2. Maintain the cookbook's quality and reliability
3. Reduce user frustration from encountering broken links

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• [ ] I have added a new entry in registry.yaml (and, optionally, in authors.yaml) so that my content renders on the cookbook website.
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  • [x] Relevance: This content is related to building with OpenAI technologies and is useful to others.
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  • [x] Correctness: The information I include is correct and all of my code executes successfully.
  • [x] Completeness: I have explained everything fully, including all necessary references and citations.