doc: Fix description of deterministic flag of CREATE COLLATION

The documentation said that you need to pick a suitable LC_COLLATE
setting in addition to setting the DETERMINISTIC flag.  This would
have been correct if the libc provider supported nondeterministic
collations, but since it doesn't, you actually need to set the LOCALE
option.

Reviewed-by: Kashif Zeeshan <kashi.zeeshan@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/a71023c2-0ae0-45ad-9688-cf3b93d0d65b%40eisentraut.org

doc/src/sgml/ref/create_collation.sgml

@@ -139,7 +139,7 @@ CREATE COLLATION [ IF NOT EXISTS ] <replaceable>name</replaceable> FROM <replace
        logically equal by the comparison.  PostgreSQL breaks ties using a
        byte-wise comparison.  Comparison that is not deterministic can make the
        collation be, say, case- or accent-insensitive.  For that, you need to
-       choose an appropriate <literal>LC_COLLATE</literal> setting
+       choose an appropriate <literal>LOCALE</literal> setting
        <emphasis>and</emphasis> set the collation to not deterministic here.
       </para>