If a term in a Mfrac has brackets around it, those brackets need to be removed


Fractions are typically output as ((a) / (b)). The extra brackets are there for safety. However, if a fraction expression is already bracketed, e.g., (a+b) over c, then we get an extra pair of brackets, i.e., (((a+b)) / (c)). These are not necessary. Also, as a refinement, if a fraction has only a single term on top or bottom (i.e., a single <mi> or <mn> element), brackets around it are not necessary either.