Update TOX_CONSTRAINTS_FILE
Update TOX_CONSTRAINTS_FILE

UPPER_CONSTRAINTS_FILE is old name and deprecated
-https://zuul-ci.org/docs/zuul-jobs/python-roles.html#rolevar-tox.tox_constraints_file
This allows to use lower-constraints file as more
readable way instead of UPPER_CONSTRAINTS_FILE=<lower-constraints file>.

[1] https://review.opendev.org/#/c/722814/

Change-Id: Ida407c05ad1026820be71ddfb84a97bcb3418df9

openstack/trove,openstack/trove