Just update @angular/core and @angular/cli by using ng update command. If you are using Angular material You have to update it as well using ng update command. If you are using older versions other than 9.

To update to the next beta or pre-release version, use the –next option. We recommend that you always update to the latest patch version, as it contains fixes we released since the initial major release. For example, use the following command to take the latest 10. x.x version and use that to update.