You can, but why, really...?.........the cream is part of the recipe and gives an unctious texture......
Seriously, the sauce works using honey as well, and you can use cornstarch to thicken if you don't want the extra fat content or you can try with a yoghurt if you like. Do not over heat the yog or the cream or c/fraiche if used as you will split the sauce and it will look and taste yukkk...
I suggest not using the cream 'cos the gnocchi soak up suaces like nothing and I would say for a lighter texture and eating, use the cornstarch to just 'glaze' the sauce instead, or simply reduce the sauce and it will thicken on its' own anyway and doesn't need extra fat........personal view though..