Fix typographical errors in documentation and comments

[Marcofann]

This PR addresses several typographical errors in documentation and inline comments across multiple files. These changes ensure grammatical accuracy and improve clarity for developers reading the code.

Files Changed:

1. kzg.rs

   • Corrected "a MPC ceremony" to "an MPC ceremony."

2. nova.rs

   • Corrected "a in-circuit compatible versions" to "an in-circuit compatible versions."

3. virtual_polynomial.rs

   • Corrected "an new virtual polynomial" to "a new virtual polynomial."

4. gadgets.rs

   • Corrected "a equality relation" to "an equality relation."

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Additional Notes

These updates are limited to documentation and comments. They do not affect the functionality of the codebase.

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Checklist

• Targeted the correct branch.
• Verified all changes are grammatical improvements.
• No changes to functionality or logic were made.

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