chore: Loosen requirement constraints

We're no longer supporting Python 3.9 and tox 4 has been around for a
long time now, it's in use in edx-platform so should be safe here.

Author: bmtcril

requirements/constraints.txt

@@ -10,9 +10,3 @@
 
 # This file contains all common constraints for edx-repos
 -c common_constraints.txt
-# tox>4.0.0 isn't yet compatible with many tox plugins, causing CI failures in almost all repos.
-# Details can be found in this discussion: https://github.com/tox-dev/tox/discussions/1810
-tox<4.0.0
-
-# Temporary to Support the python 3.11 Upgrade
-backports.zoneinfo;python_version<"3.9"  # Newer versions have zoneinfo available in the standard library