Remove pip list legacy format from documentation

Author: sbidoul

docs/html/cli/pip_list.rst

@@ -140,28 +140,6 @@ Examples
          C:\> py -m pip list --outdated --not-required
          docutils (Current: 0.10 Latest: 0.11)
 
-#. Use legacy formatting
-
-   .. tab:: Unix/macOS
-
-      .. code-block:: console
-
-         $ python -m pip list --format=legacy
-         colorama (0.3.7)
-         docopt (0.6.2)
-         idlex (1.13)
-         jedi (0.9.0)
-
-   .. tab:: Windows
-
-      .. code-block:: console
-
-         C:\> py -m pip list --format=legacy
-         colorama (0.3.7)
-         docopt (0.6.2)
-         idlex (1.13)
-         jedi (0.9.0)
-
 #. Use json formatting
 
    .. tab:: Unix/macOS