chore(deps): update circleci/postgres docker tag to v9.6.16

Author: renovate-bot

.circleci/config.yml

@@ -11,7 +11,7 @@ jobs:
         environment:
           PORT: 3000
       # CircleCI PostgreSQL images available at: https://hub.docker.com/r/circleci/postgres/
-      - image: circleci/postgres:9.6.13-alpine
+      - image: circleci/postgres:9.6.16-alpine
         environment:
           POSTGRES_USER: postgres
           POSTGRES_DB: postgres