Show the more proper message to provide info while running "acsf-tools-ml" command and there are no sites

[joshirohit100]

Steps -

• Run command say drush acsf-tools-ml updb while there are no sites available and it will give below error

[error] Impossible to fetch the list of sites. If you are not on an ACSF instance, use the --alias option.

This is because of https://github.com/acquia/acsf-tools/blob/11.x-dev/AcsfToolsCommands.php#L255