[airos] added terminal dot

Author: edoput

docs/source/backends/airos.rst

@@ -149,7 +149,7 @@ The default values for this key are as reported below
 Netmode
 -------
 
-AirOS v8.3 can operate in ``bridge`` and ``router`` mode (but defaults to ``bridge``) and this can be specified with the ``netmode`` property
+AirOS v8.3 can operate in ``bridge`` and ``router`` mode (but defaults to ``bridge``) and this can be specified with the ``netmode`` property.
 
 .. code-block:: json