ci: Fix CI not testing with Postgres 16 and flaky test (#9210)

Author: dplewis

.github/workflows/ci.yml

@@ -238,7 +238,7 @@ jobs:
             POSTGRES_IMAGE: postgis/postgis:15-3.4
             NODE_VERSION: 22.4.1
           - name: PostgreSQL 16, PostGIS 3.4
-            POSTGRES_IMAGE: postgis/postgis:15-3.4
+            POSTGRES_IMAGE: postgis/postgis:16-3.4
             NODE_VERSION: 22.4.1
       fail-fast: false
     name: ${{ matrix.name }}