Copybara auto squash

[lydhr]

Description

This PR is a simple documentation fix made to test multi-commit PR auto-squashing in Copybara (WIP b/540413134).
Specifically, it updates typos within the checkpoint conversion guide (docs/guides/checkpointing_solutions/convert_checkpoint.md).
The documentation updates include:

• Link Text Corrections
• Spelling and Grammar
• Capitalization and Formatting

Tests

These are pure documentation changes that do not affect the codebase logic. They have been verified locally by reviewing the markdown file rendering and links.

Checklist

Before submitting this PR, please make sure (put X in square brackets):

• I have performed a self-review of my code. For an optional AI review, add the gemini-review label.
• I have necessary comments in my code, particularly in hard-to-understand areas.
• I have run end-to-end tests tests and provided workload links above if applicable.
• I have made or will make corresponding changes to the doc if needed, including adding new documentation pages to the relevant Table of Contents (toctree directive) as explained in our
  documentation.

[gemini-code-assist]

Caution

The consumer version of Gemini Code Assist on GitHub has been sunset. All code review activity has officially ceased.