Cleanup comment that should've been removed

The previous change, I237f5663b0f8b060f6df130de04e17e2b1695f8a, removed
a SETUPTOOLS flag, but not the comment explaining why that flag was
previously set. Clean up that comment.

Change-Id: I32b0240fd56310d7f10596aaa8ef432679bfd66a

Author: cboylan

inc/python

@@ -186,9 +186,6 @@ function pip_install {
 
     $xtrace
 
-    # adding SETUPTOOLS_SYS_PATH_TECHNIQUE is a workaround to keep
-    # the same behaviour of setuptools before version 25.0.0.
-    # related issue: https://github.com/pypa/pip/issues/3874
     $sudo_pip \
         http_proxy="${http_proxy:-}" \
         https_proxy="${https_proxy:-}" \