Update postgres Docker tag to v15.8

etp-core/docker/docker-compose.yml

@@ -3,7 +3,7 @@ name: 'etp'
 
 services:
   db:
-    image: postgres:15.2-alpine
+    image: postgres:15.8-alpine
     command: postgres -c 'max_connections=500'
     volumes:
       - type: bind