Pin tempest version from upper-constraints

tempest.Manager has been removed in 26.1.0
(https://review.opendev.org/767628)

Related-Bug: PROD-30711
Change-Id: I870f3662679dddf8f29328b10c7fd9637dad9436
diff --git a/requirements.txt b/requirements.txt
index 3edf7dc..4b325ab 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>=17.1.0 # Apache-2.0
+tempest==25.0.1 # Apache-2.0
 tenacity>=3.2.1 # Apache-2.0
 ddt>=1.0.1 # MIT
 nose>=1.3.7 # LGPL