The SQL standard says that you should be able to write "CHARACTER SET foo"
as part of the declaration of a char-type column.  We don't implement that,
but a rough form of support has existed in gram.y since commit f10b6392.
That's now sat there for nigh 20 years without anyone fleshing it out ---
and even if someone did, the contemplated approach of having separate data
type name(s) for every character set certainly isn't what we'd do today.
Let's just remove the grammar production; if anyone is ever motivated to
work on this, reinventing the grammar support is a trivial fraction of
what they'd have to do.  And we've never documented anything about
supporting such a clause.

Per gripe from Neha Khatri.

Discussion: https://postgr.es/m/CAFO0U+-iOS5oYN5v3SBuZvfhPUTRrkDFEx8w7H17B07Rwg3YUA@mail.gmail.com