Xena: drop comment in tox.ini

Author: markgoddard

tox.ini

@@ -17,7 +17,6 @@ commands =
 [testenv:releasenotes]
 allowlist_externals = rm
 skip_install = true
-# NOTE: Using Xena upper constraints for reno 3.4.0, with support for default_branch.
 deps =
   -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/xena}
   -r{toxinidir}/releasenotes/requirements.txt