Fix indentation and class name in socket howto example.

Doc/howto/sockets.rst

@@ -180,7 +180,7 @@ righter than others).
 Assuming you don't want to end the connection, the simplest solution is a fixed
 length message::
 
-   class mysocket:
+   class MySocket:
        """demonstration class only
          - coded for clarity, not efficiency
        """