Fix/Deprecate `FmaBrotherhood` Generator

[stefannibrasil]

[related to #2787]

The generator class name has a different class name from the file name, but we would like them to match, as rthis can cause issues with autoloaders.

In order to do that, we should:

• add a new generator with the correct name
• deprecate the incorrect one

To deprecate a generator, please take a look at the documentation:
https://github.com/faker-ruby/faker/blob/main/CONTRIBUTING.md#removing-generators

[stefannibrasil]

assigned to @stephtf and @maipham5