fix: broken links in README's Suite of Physics-Informed ML Models section

[Brumbelow]

Summary

Fixed REAME.md links.

Motivation

Fixes #1303

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.
• The CHANGELOG.md is up to date with these changes.
• An issue is linked to this pull request.
• If I am implementing a new model or modifying any existing model, I have followed the Models Implementation Coding Standards.

[greptile-apps]

Greptile Summary

This PR replaces seven dead docs.nvidia.com links in the "A Suite of Physics-Informed ML Models" section of the top-level README.md with working in-repo GitHub URLs, and adds a corresponding CHANGELOG.md entry. All seven new link targets were verified to exist in the repository (e.g. physicsnemo/nn/module/gnn_layers, examples/cfd/vortex_shedding_mgn, examples/weather/corrdiff, etc.).

Important Files Changed

Filename	Overview
README.md	Seven broken links in the "A Suite of Physics-Informed ML Models" section replaced with valid in-repo GitHub paths; all new targets verified to exist in the repository.
CHANGELOG.md	Added a changelog entry for the README link fix under the correct section; wording is accurate and closes the referenced issue.

_{Reviews (1): Last reviewed commit: "Fix broken links in README's Suite of Ph..." | Re-trigger Greptile}

[Brumbelow]

Sorry @coreyjadams not sure what happened. Didn't mean to rebase. Leaving alone now