chore(deps): update postgres docker tag to v15 (#2775)

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This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| postgres | major | `14` -> `15` |

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docker-compose.yml

@@ -49,7 +49,7 @@ services:
   db:
     expose:
       - "5432"
-    image: postgres:14
+    image: postgres:15
     environment:
       # create a database called `db`
       POSTGRES_DB: "db"