It looks like this file contains a database backup/dump. Acunetix WVS inferred this filename from the domain name. A database backup contains a record of the table structure and/or the data from a database and is usually in the form of a list of SQL statements. A database backup is most often used for backing up a database so that its contents can be restored in the event of data loss. This information is highly sensitive and should never be found on a production system.
Sensitive files such as database backups should never be stored in a directory that is accessible to the web server. As a workaround, you could restrict access to this file.