Update prac 3 worksheet to reflect Postgres changes to accessing volumes.

Merge pull request #7 from CSSE6400/P3-Update.
Docker Compose prac 3 updated to reflect docker-library/postgres#1259 changes.

Author: applebyter

practicals/week03/main.tex

@@ -627,14 +627,14 @@ \subsection{Moving to a Postgresql Database}
 \begin{code}[numbers=none]{}
   services:
     database:
-      image: postgres:latest
+      image: postgres:18.3
       restart: always
       environment:
         POSTGRES_PASSWORD: verySecretPassword
         POSTGRES_USER: administrator
         POSTGRES_DB: todo
       volumes:
-        - ./data/db:/var/lib/postgresql/data
+        - ./data:/var/lib/postgresql
     app:
       build: .
       restart: always