Newline spaces are useless outside of groups

[runarberg]

As implemented newline space literals map to an <mspace> with the depth attribute set. This really only works to increase the vertical space e.g. in fractions, however fractions are implemented using an infix operator which strips the whitespace around the operator. Inside of groups (which implement e.g. matrices) the newline is a row separator so it not available there either to increase the vertical space.

So far I have found no use case for depth space which works in mathup.

We should probably find a new use for the newline outside of groups, or at the very least, remove the depth space from the output.