Bug in function `pinv`

https://github.com/josdejong/mathjs/blob/49c793ba5a47359157a2c5009e63b11e43fcff2e/src/function/matrix/pinv.js#L120

Hiya!

I was using this in my codebase, and I found that it was the source of an issue. I ended up switching to the ml-matrix implementation of pseudoinverse, which seemed to fix my problem! I see that there's a comment suggesting this be reimplemented with SVD to improve precision - it may have been that. I can't unfortunately share the code which had the issue, but I thought I'd leave a comment all the same.