docs(python): Note that only one name operation is allowed per expression

[deanm0000]

addresses the documentation part of #14010

[mcrumiller]

Is this a temporary doc change? I don't see why we shouldn't allow multiple .name operations. Related is #13858. There are currently issues when you perform operations on multiple columns simultaneously and also want to transform the names.

[deanm0000]

I guess it's temporary for as long as only one works per expression. #10782 is also relevant as it's directly asking for an enhancement to make chaining them work. Seems like the documentation should tell people that they aren't chainable.

[ritchie46]

Thank you @deanm0000. Maybe we can lift that restriction in due time. For now it is good to inform people.