Update README.md

[coreyjadams]

PhysicsNeMo Pull Request

Point out that we need matplotlib for the ring attn scaling plots.

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.

Dependencies

Review Process

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[greptile-apps]

Greptile Summary

Adds a documentation note to the ring attention example README clarifying that matplotlib is required to run the scaling plot script.

• Inserts a > Note! callout before the python plot_scaling_results.py code block, directing users to pip install matplotlib if they haven't already.

Important Files Changed

Filename	Overview
examples/minimal/ShardTensorExamples/6_ring_attention/README.md	Adds a note that matplotlib must be installed before running the scaling plot script.

_{Reviews (1): Last reviewed commit: "Update README.md" | Re-trigger Greptile}

[ktangsali]

Ideally this should have gone into RC, but since this is just a readme change, main or Rc does not matter too much.