Update Jupyter notebook kernel specification to use '.venv' and 'python3' for CI fix

[peterdsharpe]

https://nvbugspro.nvidia.com/bug/6188725

PhysicsNeMo Pull Request

Description

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.

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[greptile-apps]

Greptile Summary

This PR updates the Jupyter notebook kernel specification in tutorial_6_ml_integration.ipynb to fix a CI failure. The kernel display_name and name were referencing a custom "project" kernel that is not present in the CI environment.

• Changes kernelspec.display_name from "project" to ".venv" and kernelspec.name from "project" to "python3", aligning the notebook metadata with the virtual-environment kernel available in CI.
• No cell content, outputs, or other notebook logic is affected; this is a pure metadata fix.

Important Files Changed

Filename	Overview
examples/minimal/mesh/tutorial_6_ml_integration.ipynb	Updates kernel spec display_name from "project" to ".venv" and kernel name from "project" to "python3" to fix CI; straightforward metadata-only change.

_{Reviews (1): Last reviewed commit: "Update Jupyter notebook kernel specifica..." | Re-trigger Greptile}

[ktangsali]

Looks good, approving from my side. Would be great if @abokov-nv can verify the fix and then we can merge.

[peterdsharpe]

/blossom-ci