Doc: sync CREATE GROUP syntax synopsis with CREATE ROLE.

CREATE GROUP is an exact alias for CREATE ROLE, and CREATE USER is
almost an exact alias, as can easily be confirmed by checking the
code.  So the man page syntax descriptions ought to match up.  The
last few additions of role options seem to have forgotten to update
create_group.sgml, though.  Fix that, and add a naggy reminder to
create_role.sgml in hopes of not forgetting again.

Discussion: https://postgr.es/m/158647836143.655.9853963229391401576@wrigleys.postgresql.org

doc/src/sgml/ref/create_group.sgml

@@ -30,7 +30,10 @@ CREATE GROUP <replaceable class="parameter">name</replaceable> [ [ WITH ] <repla
     | CREATEROLE | NOCREATEROLE
     | INHERIT | NOINHERIT
     | LOGIN | NOLOGIN
-    | [ ENCRYPTED ] PASSWORD '<replaceable class="parameter">password</replaceable>'
+    | REPLICATION | NOREPLICATION
+    | BYPASSRLS | NOBYPASSRLS
+    | CONNECTION LIMIT <replaceable class="parameter">connlimit</replaceable>
+    | [ ENCRYPTED ] PASSWORD '<replaceable class="parameter">password</replaceable>' | PASSWORD NULL
     | VALID UNTIL '<replaceable class="parameter">timestamp</replaceable>'
     | IN ROLE <replaceable class="parameter">role_name</replaceable> [, ...]
     | IN GROUP <replaceable class="parameter">role_name</replaceable> [, ...]

doc/src/sgml/ref/create_role.sgml

@@ -44,6 +44,11 @@ CREATE ROLE <replaceable class="parameter">name</replaceable> [ [ WITH ] <replac
 </synopsis>
  </refsynopsisdiv>
 
+<!--
+CAUTION: remember to keep create_user.sgml and create_group.sgml
+in sync when changing the above synopsis!
+-->
+
  <refsect1>
   <title>Description</title>