Documentation small error on Forms - Subclassing forms.

[Alejandro Veintimilla]

Where it writes, near the end of the document, under Subclassing forms:

"It’s possible to declaratively remove a Field inherited from a parent class by setting the name to be None on the subclass."

it should write:

"It’s possible to declaratively remove a Field inherited from a parent class by setting the value to be None on the subclass."

[Tim Graham]

Is "name of the field" more clear? I think that's the intention of the sentence.

[Tim Graham <timograham@…>]

In 5b5a279:

Fixed #25268 -- Tweaked wording in docs/ref/forms/api.txt

[Tim Graham <timograham@…>]

In d2dfe3ae:

[1.8.x] Fixed #25268 -- Tweaked wording in docs/ref/forms/api.txt

Backport of 5b5a27942b2fa113df4d6eb3d77a33c85f58634f from master