Replace git.openstack.org URLs with opendev.org URLs

Change-Id: I1289f82c0f14b27d15f4b41b80dfe9131efb2ed7
diff --git a/tox.ini b/tox.ini
index 8dc2a65..f32dd68 100644
--- a/tox.ini
+++ b/tox.ini
@@ -5,7 +5,7 @@
 
 [testenv]
 usedevelop = True
-install_command = pip install -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt} {opts} {packages}
+install_command = pip install -c{env:UPPER_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt} {opts} {packages}
 setenv =
    VIRTUAL_ENV={envdir}
    PYTHONWARNINGS=default::DeprecationWarning