Update imap_and_smtp.rst

Insert the trigger in the proper database.

doc/integration/imap_and_smtp.rst

@@ -357,8 +357,10 @@ Copy this example into a file (for example: :file:`quota-trigger.sql`) on
 server running postgres and execute the following commands::
 
   $ su - postgres
-  $ psql < /path/to/quota-trigger.sql
+  $ psql [modoboa database] < /path/to/quota-trigger.sql
   $ exit
+  
+Replace ``[modoboa database]`` by the appropriate value.
 
 Forcing recalculation
 ---------------------