This extension used to be shipped as part of core Joomla!, but it no longer is in the version of Joomla! you are currently running.
Joomla! occasionally drops extensions which used to be part of the core installation, e.g. the “CAPTCHA - Invisible reCAPTCHA” plugin, removed in Joomla! 5. When this happens, Joomla!'s updater does NOT remove the extension from your site; it just stops shipping and updating it going forward.
As explained in more detail in Protected extensions, these extensions typically remain Protected, therefore Joomla's Extensions Manager will refuse to uninstall them. You end up with an extension that's no longer part of core Joomla!, is no longer maintained or updated by the Joomla! project, but which you also cannot remove through Joomla's own interface. This is a potential security and stability risk since bugs and vulnerabilities discovered in the extension after its removal from core will never be fixed.
Obsolete core Joomla! extensions must be uninstalled; they will never be updated again. Since they are typically Protected you cannot uninstall them using Joomla's Extensions Manager. Click the “Force Uninstall” button to remove them using Onthos.
Onthos determines whether an extension is an obsolete core extension by comparing it against its own internal list of Joomla! core extensions and the range of Joomla! versions each one of them shipped with. This list is periodically refreshed as new Joomla! versions are released.
The only exception to this check is the en-GB English (United Kingdom) language pack. Since Joomla! 4, it is no longer part of Joomla!'s own installation and update files, even though it's still installed as a core extension; without this exception it would always –and wrongly– appear as obsolete.