writing/tests.rst: Unbold “mock”

Author: Zearin

docs/writing/tests.rst

@@ -251,7 +251,7 @@ the need to change any other code.
 mock
 ----
 
-**``mock``** is a library for testing in Python. As of Python 3.3, it is 
+``mock`` is a library for testing in Python. As of Python 3.3, it is 
 available in the `standard library <http://docs.python.org/dev/library/unittest.mock`_.  
 
 For older versions of Python: