Switch back the tox constraint to master

Tempest 42.0.0 release hash is prepared[1] so we can
revert back to use the master constraints by default.

[1] https://review.opendev.org/c/openstack/tempest/+/933772/1

Change-Id: I5267cc99d1ad6572fc8546d0338f25e7fad01481
diff --git a/tox.ini b/tox.ini
index 199265a..e3c8fcf 100644
--- a/tox.ini
+++ b/tox.ini
@@ -9,7 +9,7 @@
     OS_TEST_PATH=./tempest/test_discover
     OS_TEST_TIMEOUT={env:OS_TEST_TIMEOUT:1200}
 deps =
-    -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/2024.2}
+    -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
     -r{toxinidir}/requirements.txt
 
 [testenv]
@@ -40,7 +40,7 @@
 allowlist_externals =
     find
 deps =
-    -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/2024.2}
+    -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
     -r{toxinidir}/requirements.txt
     -r{toxinidir}/test-requirements.txt
 commands =
@@ -337,7 +337,7 @@
 
 [testenv:venv]
 deps =
-  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/2024.2}
+  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/requirements.txt
   -r{toxinidir}/doc/requirements.txt
 commands = {posargs}
@@ -351,7 +351,7 @@
 
 [testenv:docs]
 deps =
-  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/2024.2}
+  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/doc/requirements.txt
 commands =
   sphinx-apidoc -f -o doc/source/tests/compute tempest/api/compute
@@ -440,7 +440,7 @@
 
 [testenv:releasenotes]
 deps =
-  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/2024.2}
+  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/doc/requirements.txt
 commands =
   rm -rf releasenotes/build