app_lua: typo in register parameter

- note about submodule sr.auth_db

modules/app_lua/README

@@ -128,6 +128,8 @@ modparam("lua", "load", "/usr/local/etc/kamailio/lua/myscript.lua")
    Use this function to register optional SIP Router submodules to Lua.
    Available submodules are:
      * auth - register functions from auth module under 'sr.auth'.
+     * auth_db - register functions from auth_db module under
+       'sr.auth_db'.
      * rr - register functions from rr module under 'sr.rr'.
      * sqlops - register functions from sqlops module under 'sr.sqlops'.
      * sl - register functions from sl module under 'sr.sl'.
@@ -140,7 +142,7 @@ modparam("lua", "load", "/usr/local/etc/kamailio/lua/myscript.lua")
 
    Example 1.2. Set register parameter
 ...
-modparam("lua", "register", "sr")
+modparam("lua", "register", "sl")
 ...
 
 4. Exported Functions

modules/app_lua/doc/app_lua_admin.xml

@@ -115,6 +115,12 @@ modparam("lua", "load", "/usr/local/etc/kamailio/lua/myscript.lua")
 				under 'sr.auth'.
 			</para>
 		    </listitem>
+		    <listitem>
+			<para>
+				<emphasis>auth_db</emphasis> - register functions from auth_db
+				module under 'sr.auth_db'.
+			</para>
+		    </listitem>
 		    <listitem>
 			<para>
 				<emphasis>rr</emphasis> - register functions from rr module
@@ -153,7 +159,7 @@ modparam("lua", "load", "/usr/local/etc/kamailio/lua/myscript.lua")
 		<title>Set <varname>register</varname> parameter</title>
 		<programlisting format="linespecific">
 ...
-modparam("lua", "register", "sr")
+modparam("lua", "register", "sl")
 ...
 </programlisting>
 	    </example>