Correct example syntax and whitespace

Corrects some examples and remove trailing whitespace in
the Heat Resource Plug-in Development Guide
page (pluginguide.html)

Closes-Bug: 1350503

Change-Id: I34b142e950b9a4588b415d44274732d835cfd8f4

doc/source/pluginguide.rst

@@ -123,14 +123,13 @@ plug-in.
                 ]
             )
         }
-        
         properties_schema = {
             "property_name": properties.Schema(
                 properties.Schema.MAP,
                 _('Internationalized description of property'),
                 required=True,
                 default={"Foo": "Bar"},
-                schema": nested_schema
+                schema=nested_schema
             )
         }