I'm not aware of any way of doing so directly within Google Colaboratory, however a usable workaround might be to install a third party spell-checking browser plug-in such as Grammarly or another similar plug-in that works with your preferred browser, I know this probably wasn't the answer you where looking for, but I'm not aware of any better solutions, I truly apologize! But I hope this was at least somewhat helpful! Sorry I can't be of more help!