bpo-38928: Remove upgrade_dependencies() from venv doc (GH-17410)

Author: uranusjr

Doc/library/venv.rst

@@ -186,14 +186,6 @@ creation according to their needs, the :class:`EnvBuilder` class.
         Installs activation scripts appropriate to the platform into the virtual
         environment.
 
-    .. method:: upgrade_dependencies(context)
-
-       Upgrades the core venv dependency packages (currently ``pip`` and
-       ``setuptools``) in the environment. This is done by shelling out to the
-       ``pip`` executable in the environment.
-
-       .. versionadded:: 3.8
-
     .. method:: post_setup(context)
 
         A placeholder method which can be overridden in third party