Typo in sparse/linalg.jl

[Scott Jones]

I ran across this, while working on my "julia-lite" branch:

function factorize(A::SparseMatrixCSC)
    m, n = size(A)
    if m == n
        if istril(A)
            if istriu(A)
                return return Diagonal(A)

it's around line 840.

I'd submit a PR to fix this, but since I'm no longer permitted to do so... I thought I'd mention it here so somebody else can fix it.