Remove useless unconstify

Digging into the history, this was not necessary even when it was
added, but might have been some time before that.  In any case, there
is no use for this now.

src/backend/utils/adt/formatting.c

@@ -2621,7 +2621,7 @@ seq_search_localized(const char *name, char **array, int *len, Oid collid)
 	 * Fold to upper case, then to lower case, so that we can match reliably
 	 * even in languages in which case conversions are not injective.
 	 */
-	upper_name = str_toupper(unconstify(char *, name), strlen(name), collid);
+	upper_name = str_toupper(name, strlen(name), collid);
 	lower_name = str_tolower(upper_name, strlen(upper_name), collid);
 	pfree(upper_name);