Update PostgreSQL image to latest and adjust volume path for data persistence

Author: sireeshajonnalagadda

src/ruby-rails-postgres/.devcontainer/docker-compose.yml

@@ -30,8 +30,6 @@ services:
     # (Adding the "ports" property to this file will not forward from a Codespace.)
 
   db:
-    # Use PostgreSQL 16 Alpine for stability and smaller image size
-    # Pinned version avoids PostgreSQL 18+ compatibility issues with data directory format
     image: postgres:latest
     restart: unless-stopped
     networks: