Fix typo in unittest.mock documentation: manger -> manager (GH-12352)

Author: massich

Doc/library/unittest.mock.rst

@@ -1440,7 +1440,7 @@ passed by keyword *after* any of the standard arguments created by :func:`patch`
     >>> test_function()
 
 If :func:`patch.multiple` is used as a context manager, the value returned by the
-context manger is a dictionary where created mocks are keyed by name::
+context manager is a dictionary where created mocks are keyed by name::
 
     >>> with patch.multiple('__main__', thing=DEFAULT, other=DEFAULT) as values:
     ...     assert 'other' in repr(values['other'])