Bump actions/checkout from v6 to v7 in /.github/workflows

[UltralyticsAssistant]

Bump actions/checkout from v6 to v7 in /.github/workflows

This PR updates GitHub Actions references in this repository.

Examples:

• Branch: actions/checkout@main stays on @main
• Major tag: actions/checkout@v4 updates to @v5
• Specific tag: astral-sh/setup-uv@v0.5.0 updates to @v0.9.4
• SHA pinned: actions/checkout@<sha> # v4.1.0 updates to the latest release SHA and tag comment

_{Made with ❤️ by Ultralytics Actions}

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

🔄 This PR updates the GitHub Actions checkout step in CI from actions/checkout@v6 to actions/checkout@v7.

📊 Key Changes

• Upgraded the CI workflow in .github/workflows/ci.yml
• Replaced actions/checkout@v6 with actions/checkout@v7
• No application code or model behavior was changed; this is a workflow maintenance update 🛠️

🎯 Purpose & Impact

• Improves CI workflow maintenance by keeping GitHub Actions dependencies up to date ✅
• Helps ensure better compatibility with the latest GitHub Actions ecosystem
• May provide security, reliability, or performance improvements from the newer action version 🔒
• Has little to no direct impact on end users, but can make automated testing and development workflows more stable for contributors 🚀

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!