Make 'Overall Comments' section of performance review form non-mandatory

The 'Overall Comments' section of the performance review form currently has to be populated before the form can be shared with the manager. As specific review questions are already set up for the user to answer, it may be that there is no extra narrative for the user to add to the overall comments section (which we have found is the case for a few of our users). Is there any way this particular question can be made a non-mandatory field otherwise users have to think up some irrelevant text to add in just to be able to proceed in sharing the form.