With Kali (and many other Linux distributions), upgrades are typically handled by the distributions themselves using the package manager (unless you are building from source) and will update to the latest version available in the distribution, which may not match our most recent release (there is usually a lag time between the two, that is normal). With Kali in particular, the preferred way to keep applications up to date is to keep the system up to date (they use a rolling release model).
One quick question on the error message, there are different types (application, feed status and scripts). Can you please post a screenshot or the text of the full error message to make sure we are talking about the same thing? Thanks
This means that the used openvas-scanner package hasn’t been updated to the latest available version 21.4.4-1 from kali-rolling and is still at version 21.4.3.