Correct column name in information schema

Although the standard has routines.result_cast_character_set_name, given
the naming of the surrounding columns, we concluded that this must have
been a mistake and that result_cast_char_set_name was intended, so
change the implementation.  The documentation was already using the new
name.

found by Clément Prévost <prevostclement@gmail.com>

src/backend/catalog/information_schema.sql

@@ -1471,7 +1471,7 @@ CREATE VIEW routines AS
            CAST(null AS cardinal_number) AS result_cast_char_octet_length,
            CAST(null AS sql_identifier) AS result_cast_char_set_catalog,
            CAST(null AS sql_identifier) AS result_cast_char_set_schema,
-           CAST(null AS sql_identifier) AS result_cast_character_set_name,
+           CAST(null AS sql_identifier) AS result_cast_char_set_name,
            CAST(null AS sql_identifier) AS result_cast_collation_catalog,
            CAST(null AS sql_identifier) AS result_cast_collation_schema,
            CAST(null AS sql_identifier) AS result_cast_collation_name,