requires os-traits >= 2.9.0

Without the latest version, nova fails many unit tests (it failed
with os-traits 2.7.0 at least).

Closes-Bug: #1990121
Change-Id: I6b320ae1f9058aaa5bac91c7c7ca60136e0cee5c
(cherry picked from commit 6a06a57)

Author: thomasgoirand

requirements.txt

@@ -53,7 +53,7 @@ psutil>=3.2.2 # BSD
 oslo.versionedobjects>=1.35.0 # Apache-2.0
 os-brick>=5.2 # Apache-2.0
 os-resource-classes>=1.1.0 # Apache-2.0
-os-traits>=2.7.0 # Apache-2.0
+os-traits>=2.9.0 # Apache-2.0
 os-vif>=1.15.2 # Apache-2.0
 castellan>=0.16.0 # Apache-2.0
 microversion-parse>=0.2.1 # Apache-2.0