Pin tempest version correctly

Do not specify exact version, use constraint.

Change-Id: Ica1954465583b4bccd8912aef0482cc96ee27347
Related-Prod: PRODX-3456
diff --git a/requirements.txt b/requirements.txt
index 4b325ab..804ce9f 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -12,7 +12,7 @@
 oslo.utils>=3.33.0 # Apache-2.0
 paramiko>=2.0.0 # LGPLv2.1+
 six>=1.10.0 # MIT
-tempest==25.0.1 # Apache-2.0
+tempest<26.0.0 # Apache-2.0
 tenacity>=3.2.1 # Apache-2.0
 ddt>=1.0.1 # MIT
 nose>=1.3.7 # LGPL