Disconnect the specified site from the specified hub site

• command: spo hubsite disconnect -s|--siteUrl <siteUrl> --confirm
• siteUrl: absolute URL of the site collection to disconnect from its hub site
• confirm: disconnects the site from its hub site without prompting for confirmation first
• requires connection to the SharePoint tenant admin site

For more information see the Disconnect-SPOHubSite cmdlet in the November release of the SPO PowerShell.