[Doc] Fix tox command option to run smoke tests

This commit fixes the tox command option to run the smoke tests. The
original arguments fail with the error[1], and `-efull` and
`tempest.scenario.test_network_basic_ops` are not for the smoke tests.

[1]
 $ tox -efull tempest.scenario.test_network_basic_ops
 ...
 tempest run: error: unrecognized arguments: tempest.scenario.test_network_basic_ops

Change-Id: I9c3dd9fb4f64bf856c5cab88a2aeaae355c84a65

Author: masayukig

doc/source/configuration.rst

@@ -636,7 +636,7 @@ tests can be run as follows:
 ::
 
     $ cd /opt/stack/tempest
-    $ tox -efull  tempest.scenario.test_network_basic_ops
+    $ tox -e smoke
 
 By default tempest is downloaded and the config file is generated, but the
 tempest package is not installed in the system's global site-packages (the