You can do so with the Loco Translate plugin. I just tried it and it works fine π Keep in mind that this text is coming from WordPress and not GeneratePress (or any theme); the theme just controls how it looks.
Unfortunately, it’s not a “text” file but in one of the core WP php files, the editing of which is not recommended as they will be negated on the next update.
Once you do the edit with Loco Translate, you can delete the plugin as it creates a file with the change that is update safe π