Update MSLearn paths to include more recent features

Based on this comment under #14766:

> agree. In the past months I gave task to several engineers about user defined types and none of them has done it. And it is just one google search away at least to understand what they are. I have done the ms learn courses recently on bicep and I think they are not there as well if I remember correctly.
>
> _Originally posted by @slavizh in https://github.com/Azure/bicep/issues/14766#issuecomment-2274988310_