Upgrade prometheus-postgres-exporter (v0.14.0-3 -> v0.14.0-4)

The new version drops support for the legacy basic auth method
(`prometheus_postgres_exporter_basicauth_*` variables).

requirements.yml

@@ -52,7 +52,7 @@
   version: v1.7.0-3
   name: prometheus_node_exporter
 - src: git+https://github.com/mother-of-all-self-hosting/ansible-role-prometheus-postgres-exporter.git
-  version: v0.14.0-3
+  version: v0.14.0-4
   name: prometheus_postgres_exporter
 - src: git+https://gitlab.com/etke.cc/roles/redis.git
   version: v7.2.3-2