Remove `DREVOPS_DB_DOWNLOAD_SSH_FILE` from the `.env.local.default`.

[AlexSkrypnyk]

In most cases, the SSH key file is the same for all operations that require SSH file.

Some work has been done to abstract SSH setup into a setup-ssh.sh script. This script is called from other scripts with a specific prefix, allowing to load script-specific env variables for a key OR use a default key.

The .env.local.default still has a variable set for the default DB download file pointing to a default value. This is no longer required to be present in that file and should be removed.

Solution direction

1. Remove the following from the .env.local.default file.

# SSH key file used to access Lagoon environment to download the database.
# Create an SSH key and add it to your account in the Lagoon Dashboard.
DREVOPS_DB_DOWNLOAD_SSH_FILE=$HOME/.ssh/id_rsa

2. Update docs for variables: cd .scaffold && ahoy update-docs