Update postgres Docker tag to v16 (#118)

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This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| postgres | major | `12` -> `16` |

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docker-compose.yml

@@ -2,7 +2,7 @@ version: "3.7"
 
 services:
   db:
-    image: postgres:12
+    image: postgres:16
     environment:
       - POSTGRES_PASSWORD=postgres
       - POSTGRES_USER=postgres