ci(tests): pin pytest (#2362)

With pytest-8.1.0 it has been discovered that there are breaking changes
which affect flexmock (flexmock/flexmock#152).

This release has already been “yanked” from the pip, yet it's making our
life miserable, so pin the pytest to the last working version until this
mess is resolved.

files/recipe-tests.yaml

@@ -16,7 +16,7 @@
       ansible.builtin.pip:
         name:
           - requre
-          - pytest
+          - pytest==8.0.2
           - pytest-cov
           - pytest-flask
           - deepdiff