fix(create-rsbuild): remove public/.gitkeep file

[chenjiahan]

Summary

We added a .gitkeep file to the templates to demonstrate the use of the public directory. But it will generate a dist/.gitkeep file and might confuse users.

This PR removes the public/.gitkeep file and we will add a public/favicon.ico to the templates later.

Related Links

resolve #4666

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

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