[ws_health_exporter] pin marshmallow to exact version for consistency

Author: eduardspa

roles/ws_health_exporter/tasks/main.yml

@@ -38,7 +38,7 @@
           - apscheduler==3.10.1
           - flask==3.0.0
           - environs==9.5.0
-          - marshmallow<4
+          - marshmallow==3.26.2
           - waitress==2.1.2
         virtualenv: "{{ _ws_health_exporter_venv }}"
         virtualenv_command: python3 -m venv