Issue #21034: Remove outdated paragraph from venv documentation

Since Python 3.4, there is no need to install pip and setuptools
into a venv manually.

Doc/library/venv.rst

@@ -43,11 +43,6 @@ Creating virtual environments
    Common installation tools such as ``Setuptools`` and ``pip`` work as
    expected with venvs - i.e. when a venv is active, they install Python
    packages into the venv without needing to be told to do so explicitly.
-   Of course, you need to install them into the venv first: this could be
-   done by running ``ez_setup.py`` with the venv activated,
-   followed by running ``easy_install pip``. Alternatively, you could download
-   the source tarballs and run ``python setup.py install`` after unpacking,
-   with the venv activated.
 
    When a venv is active (i.e. the venv's Python interpreter is running), the
    attributes :attr:`sys.prefix` and :attr:`sys.exec_prefix` point to the base