Bump pytest to version 8.3.4

This has been causing unittest failures in some projects, bump this in a
dedicated patch to allow proper verification.

Depends-On: https://review.opendev.org/c/openstack/horizon/+/939389
Change-Id: I86a1b6dbe744d83114a9a9c9ad9f172eea9afc86

Author: osfrickler

upper-constraints.txt

@@ -30,7 +30,7 @@ lxml===5.3.0
 vintage===0.4.1
 rst2txt===1.1.0
 setproctitle===1.3.4
-pytest===8.1.2
+pytest===8.3.4
 python-slugify===8.0.4
 cursive===0.2.3
 oslo.service===3.6.0