title: Replacement for from_2d_array_to_nested() in sktime
body: <p>I recently updated my sktime package (to version '0.13.2'), and my old code which uses from_2d_array_to_nested() is not working anymore. I need to format data to feed it to the mini rocket model. Can someone please tell me what function I can use to process my data? I am stuck at work because of this!!!</p>