[PROPOSAL] Skip test citext_utf8 on Windows

Greetings, everyone!

While running "installchecks" on databases with UTF-8 encoding the test
citext_utf8 fails because of Turkish dotted I like this:

  SELECT 'i'::citext = 'İ'::citext AS t;
   t
  ---
- t
+ f
  (1 row)

I tried to replicate the test's results by hand and with any collation
that I tried (including --locale="Turkish") this test failed

Also an interesing result of my tesing. If you initialize you DB
with -E utf-8 --locale="Turkish" and then run select LOWER('İ');
the output will be this:
  lower
-------
  İ
(1 row)

Which I find strange since lower() uses collation that was passed
(default in this case but still)

My PostgreSQL version is this:
postgres=# select version();
                                version
----------------------------------------------------------------------
  PostgreSQL 17devel on x86_64-windows, compiled by gcc-13.1.0, 64-bit

The proposed patch for skipping test is attached

Oleg Tselebrovskiy, Postgres Pro