Update the "utilities" documentation page

[Amxx]

Fixes #4673

This should be cherrypicked on top of the docs branch.

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• Documentation

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[ernestognw]

I think we need to remove all the Payments section altogether, it's empty now!
Similarly, we're referencing SafeMath a couple of lines above

[Amxx]

The rest of the "Payments" option is not related to our utils, but its still usefull information. Maybe we should move it to the "Address" part ?

[ernestognw]

I readded the Math section describing what's featuring there. Regarding the "Payments" not, I just checked in Address and we're already very clear about reentrancies. I think that section served as an introduction before but now it doesn't make sense to keep it imo.