Upgrade process 1.8.1 -> 1.9.0 redefines _APP_DB_HOST on .env file

### 👟 Reproduction steps I use a MariaDB database hosted elsewhere, not the one defined in the `docker-compose.yml` file. So, I set the `_APP_DB_HOST` variable in the `.env` file to use that DB. During the upgrade process, however, the script overwrote that variable with the default `mariadb` value, pointing to the database container of the `docker-compose` file. That way, the migration process of the web installer was not executed in the actual database, but probably in an empty database generated when initializing the containers. ### 👍 Expected behavior The upgrade script should not, in my opinion, overwrite that variable. I don't know if that's intended behavior. ### 👎 Actual Behavior Environment variable overwritten, leading to migration not executing. ### 🎲 Appwrite version Different version (specify in environment) ### 💻 Operating system Linux ### 🧱 Your Environment Appwrite self-hosted 1.9.0 ### 👀 Have you spent some time to check if this issue has been raised before? - [x] I checked and didn't find similar issue ### 🏢 Have you read the Code of Conduct? - [x] I have read the [Code of Conduct](https://github.com/appwrite/.github/blob/main/CODE_OF_CONDUCT.md)