Remove old comments in dependencies.c and README.dependencies

Hi,

I found some comments which are not implemented.

As far as I have examined, these comments refer to min_group_size,
but min_group_size was decided not to adopt and removed[1], so
it seems these comments also should be removed.

[1]
https://www.postgresql.org/message-id/CAKJS1f_vUck+qbxqsh4m_FNs+D4XA2KPyvvh0zYMjVg-eEHeAQ@mail.gmail.com

>>> 1) DEPENDENCY_MIN_GROUP_SIZE
>>>
>>> I'm not sure we still need the min_group_size, when evaluating
>>> dependencies. It was meant to deal with 'noisy' data, but I think it
>>> after switching to the 'degree' it might actually be a bad idea.
>
>Yeah, I'd wondered about this when I first started testing the patch.
>I failed to get any functional dependencies because my values were too
>unique. Seems I'd gotten a bit used to it, and in the end thought that
>if the values are unique enough then they won't suffer as much from
>the underestimation problem you're trying to solve here.
>
>I've removed that part of the code now.

Attached patch removes the comments about min_group_size.

Regards,

--
Atsushi Torikoshi
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center