Correct copy-paste error in CustomField schema

[highfalutin]

Before: in API4 explorer and elsewhere, the description for CustomField.name is a verbatim copy of CustomGroup.name -- this is incorrect

After: description correctly refers to "field"

[civibot]

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[eileenmcnaughton]

Well spotted @highfalutin - this is so trivial I'm happy just merge as is & let the DAO get fixed 'when it does' - but to make this change show up you will need to run GenCode.php (I run it by going into the xml dir & running php Gencode.php although I think @seamuslee001 has a more recommended way - it might even be documented).

I'll merge this & you can put that up as a patch now or it can happen when it happens