docker-compose: fix dev setup

My fix for this here https://github.com/ecamp/ecamp3/pull/5560/files#r1735167412
for the merge conflict with #5372
was a little short-sighted.

Author: BacLuc

docker-compose.override.yml

@@ -11,6 +11,7 @@ services:
       - ./api/docker/php/docker-entrypoint.sh:/usr/local/bin/docker-entrypoint:delegated
       - ./.cache/composer:/tmp/composer/cache:delegated
     environment:
+      DATABASE_URL: "postgresql://ecamp3:ecamp3@database:5432/ecamp3?serverVersion=15&charset=utf8"
       # See https://docs.docker.com/docker-for-mac/networking/#i-want-to-connect-from-a-container-to-a-service-on-the-host
       # See https://github.com/docker/for-linux/issues/264
       # The `remote_host` below may optionally be replaced with `remote_connect_back`