Fix markup to not add parens to the "hashlib.md5" constructor when the object...

Fix markup to not add parens to the "hashlib.md5" constructor when the object is meant, not the call.

Doc/library/hmac.rst

@@ -20,7 +20,7 @@ This module implements the HMAC algorithm as described by :rfc:`2104`.
 
    Return a new hmac object.  If *msg* is present, the method call ``update(msg)``
    is made. *digestmod* is the digest constructor or module for the HMAC object to
-   use. It defaults to  the :func:`hashlib.md5` constructor.
+   use. It defaults to  the :data:`hashlib.md5` constructor.
 
 
 An HMAC object has the following methods: