hook_field_group_build_pre_render_alter() is not called since 3.x

For anyone who hits this issue, I'm not sure that this is a bug so much as a documentation problem.

The API is different from the Drupal 7 version. If you want to mess with field groups on forms, you want hook_field_group_form_process() (to alter individual field groups) or hook_field_group_form_process_build() (to alter any of the available field groups).

The description and sample code in hook_field_group_build_pre_render_alter() in field_group.api.php is pretty clearly wrong and should be conformed to the implementation in field_group_field_group_build_pre_render_alter().

The hook_field_group_build_pre_render_alter is still used, but only in the entity view context. It idd used to work also with forms, but the form handling was moved to the processing part.

I modified the api example.

Thanks for fixing it!