add missing immutable keyword to server management examples (neo4j#1932)

Author: phil198

modules/ROOT/pages/authentication-authorization/dbms-administration.adoc

@@ -1289,13 +1289,13 @@ For more details about the syntax descriptions, see xref:database-administration
 | Command | Description
 
 | [source, syntax, role=noheader]
-GRANT SERVER MANAGEMENT
+GRANT [IMMUTABLE] SERVER MANAGEMENT
   ON DBMS
   TO role[, ...]
 | Enables the specified roles to show, enable, rename, alter, reallocate, deallocate, and drop servers.
 
 | [source, syntax, role=noheader]
-GRANT SHOW SERVERS
+GRANT [IMMUTABLE] SHOW SERVERS
   ON DBMS
   TO role[, ...]
 | Enables the specified roles to show servers.