[DOCS] Reveal operation has been renamed to to_public()

[navasvarela]

Thank you for reading the docs and suggesting an improvement!

First things first

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**What section of the docs could be improved? **
Nada Lang Operators, perhaps also Reveal section in Nada By Example Reveal

What part(s) of the docs would you like to see updated?
The reveal operation has been renamed to to_public() recently

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