Fix wrong syntax about CREATE_REPLICATION_SLOT

Hi hackers,

A minor bug was found in the "CREATE_REPLICATION_SLOT" syntax.
It is in protocol.sgml at line 1990.

The current syntax written in it is as follows,

CREATE_REPLICATION_SLOT slot_name [ TEMPORARY ] { PHYSICAL | LOGICAL } [ ( option [, ...] ) ]

However, when I executed a command as follows, that became syntax error.

CREATE_REPLICATION_SLOT tachi LOGICAL;
ERROR: syntax error

To use LOGICAL, output_plugin must be required.
Correct syntax is as follows.

CREATE_REPLICATION_SLOT slot_name [ TEMPORARY ] { PHYSICAL | LOGICAL output_plugin } [ ( option [, ...] ) ]

PSA patch to fix it.

Note that version 15 must also be fixed.

Best Regards,
Ayaki Tachikake
FUJITSU LIMITED