Change mention of '/load omemo' to 'plugin_autload' because of poezio/slixmpp-omemo#10

Signed-off-by: Maxime “pep” Buquet <pep@bouah.net>

README.rst

@@ -7,12 +7,11 @@ distributed separately for licensing reasons.
 Use in poezio
 -------------
 
-Once installed (see the `Installation`_ section below), `/load omemo` in
-Poezio.
-
-See the Poezio `documentation
+Once installed (see the `Installation`_ section below), you can add
+`omemo` in the `plugin_autoload` configuration. See the Poezio
+`documentation
 <https://doc.poez.io/plugins/index.html#plugin-autoload>`_ for more
-information.
+information about autoloading plugins.
 
 License
 -------