Clean up additional INSTALL_TESTONLY_PACKAGES bits

The original removal is in https://review.openstack.org/#/c/167669/

Change-Id: I3c59f040523d2cd1453465e80280955218880634
diff --git a/inc/python b/inc/python
index d00eb0c..39684b6 100644
--- a/inc/python
+++ b/inc/python
@@ -53,7 +53,7 @@
 }
 
 # Wrapper for ``pip install`` to set cache and proxy environment variables
-# Uses globals ``INSTALL_TESTONLY_PACKAGES``, ``OFFLINE``, ``PIP_VIRTUAL_ENV``,
+# Uses globals ``OFFLINE``, ``PIP_VIRTUAL_ENV``,
 # ``PIP_UPGRADE``, ``TRACK_DEPENDS``, ``*_proxy``
 # pip_install package [package ...]
 function pip_install {