doc: Fix description of replication command CREATE_REPLICATION_SLOT

The output plugin name is a mandatory option when creating a logical
slot, but the grammar documented was not described as such.  While on
it, fix two comments in repl_gram.y to show that TEMPORARY is an
optional grammar choice.

Author: Ayaki Tachikake
Discussion: https://postgr.es/m/OSAPR01MB2852607B2329FFA27834105AF1229@OSAPR01MB2852.jpnprd01.prod.outlook.com
Backpatch-through: 15

Author: michaelpq

doc/src/sgml/protocol.sgml

@@ -1987,7 +1987,7 @@ psql "dbname=postgres replication=database" -c "IDENTIFY_SYSTEM;"
     </varlistentry>
 
     <varlistentry id="protocol-replication-create-replication-slot" xreflabel="CREATE_REPLICATION_SLOT">
-     <term><literal>CREATE_REPLICATION_SLOT</literal> <replaceable class="parameter">slot_name</replaceable> [ <literal>TEMPORARY</literal> ] { <literal>PHYSICAL</literal> | <literal>LOGICAL</literal> } [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ]
+     <term><literal>CREATE_REPLICATION_SLOT</literal> <replaceable class="parameter">slot_name</replaceable> [ <literal>TEMPORARY</literal> ] { <literal>PHYSICAL</literal> | <literal>LOGICAL</literal> <replaceable class="parameter">output_plugin</replaceable> } [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ]
       <indexterm><primary>CREATE_REPLICATION_SLOT</primary></indexterm>
      </term>
      <listitem>

src/backend/replication/repl_gram.y

@@ -172,7 +172,7 @@ base_backup:
 			;
 
 create_replication_slot:
-			/* CREATE_REPLICATION_SLOT slot TEMPORARY PHYSICAL [options] */
+			/* CREATE_REPLICATION_SLOT slot [TEMPORARY] PHYSICAL [options] */
 			K_CREATE_REPLICATION_SLOT IDENT opt_temporary K_PHYSICAL create_slot_options
 				{
 					CreateReplicationSlotCmd *cmd;
@@ -183,7 +183,7 @@ create_replication_slot:
 					cmd->options = $5;
 					$$ = (Node *) cmd;
 				}
-			/* CREATE_REPLICATION_SLOT slot TEMPORARY LOGICAL plugin [options] */
+			/* CREATE_REPLICATION_SLOT slot [TEMPORARY] LOGICAL plugin [options] */
 			| K_CREATE_REPLICATION_SLOT IDENT opt_temporary K_LOGICAL IDENT create_slot_options
 				{
 					CreateReplicationSlotCmd *cmd;