We are all aware of the feature of upgrading our classic apps to lightning version so that we can achieve the benefits of lightning apps.
But I am not able to see Upgrade option for one of my app named Content. It is a standard app and it is available in lightning also. But I am not having an option to upgrade this app to lightning version so that I can keep two versions of this app each for Classic and Lightning.
Any help is much appreciated.
See the screenshot below: