Heroku app.json: Use Postgres 16 (#443)

dbackeus · web-flow · commit aad82d9ab2fe · 2024-08-13T16:26:54.000-04:00
Since Postgres 13 is deprecated.
diff --git a/app.json b/app.json
@@ -38,7 +38,7 @@
     {
       "plan": "heroku-postgresql",
       "options": {
-        "version": "13"
+        "version": "16"
       }
     }
  ]
