Deployment: Fly.io Hobby plan pricing update

[BKM14]

Because

Fly.io doesn't offer the free $5 credit anymore. It has completely transitioned to a paid-only model.

This PR

• Rewrite the text with updated pricing.

Issue

Closes #28967

Additional Information

Pull Request Requirements

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• The title of this PR follows the location of change: brief description of change format, e.g. Intro to HTML and CSS lesson: Fix link text
• The Because section summarizes the reason for this PR
• The This PR section has a bullet point list describing the changes in this PR
• If this PR addresses an open issue, it is linked in the Issue section
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• If any lesson files are included in this PR, they follow the Layout Style Guide

[BKM14]

@JoshDevHub, can you review this please?
Thank you

[MaoShizhong]

Related: #28862 & #28491

[JoshDevHub]

Thank you for contributing and making these changes 🚀

In the future, if you're working on an issue, please comment on the issue saying that you'd like to work on it and wait for a maintainer to assign it to you. This helps prevent duplicate or unnecessary work that might waste your time. Hopefully that makes sense.