[FIX] web_widget_x2many_2d_matrix: RST syntax

web_widget_x2many_2d_matrix/README.rst

@@ -123,6 +123,8 @@ Known issues / Roadmap
 * If you pass values with an onchange, you need to overwrite the model's method
   `onchange` for making the widget work::
 
+ .. code-block:: python
+
     @api.multi
     def onchange(self, values, field_name, field_onchange):
         if "one2many_field" in field_onchange:
@@ -130,6 +132,7 @@ Known issues / Roadmap
                 field_onchange.setdefault("one2many_field." + sub, u"")
         return super(model, self).onchange(values, field_name, field_onchange)
 
+
 Bug Tracker
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