pgsql: Adjust comments about collate.linux.utf8 regression test.

Adjust comments about collate.linux.utf8 regression test.

This test should now work in any database with UTF8 encoding, regardless
of the database's default locale.  The former restriction was really
"doesn't work if default locale is C", and that was because of not handling
mbstowcs/wcstombs correctly.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/1abd146dddc1dc5efff5ccac065c460108acbaa9

Modified Files
--------------
doc/src/sgml/regress.sgml                        |    2 +-
src/test/regress/expected/collate.linux.utf8.out |    3 ++-
src/test/regress/sql/collate.linux.utf8.sql      |    3 ++-
3 files changed, 5 insertions(+), 3 deletions(-)