`normest` broken for non-square matrices

I tried using `normest` for a non-square matrix and was prompted with a dimension error. I believe in this line, the `n` should be changed to an `m` since the operator `S` has size `(m,n)`.

https://github.com/JuliaSmoothOptimizers/LinearOperators.jl/blob/0295c2002e7a5c28733f0586c2c3c1e2618b8258/src/utilities.jl#L39