Update http_client.rst

Co-authored-by: Nicolas Grekas <[email protected]>

Author: mpdude

http_client.rst

@@ -2289,7 +2289,7 @@ set the ``error`` option value when creating the ``MockResponse``.
 Transport errors of this kind occur, for example, when a host name
 cannot be resolved or the host was unreachable. The
 ``TransportException`` will be thrown as soon as a method like
-``getStatusCode()`` or ``getContent()`` is called.
+``getStatusCode()`` or ``getHeaders()`` is called.
 
 In order to test errors that occur while a response is being streamed
 (that is, after the headers have already been received), provide the