Remove boxing in pinv (#51351)

As discussed in
https://discourse.julialang.org/t/pinv-not-type-stable/103885/14, the
`tol` variable is captured which leads to it being boxed, as suggested
can be fixed by having two separate variables.

stdlib/LinearAlgebra/src/dense.jl

@@ -1483,10 +1483,10 @@ function pinv(A::AbstractMatrix{T}; atol::Real = 0.0, rtol::Real = (eps(real(flo
  return B
  end
  SVD = svd(A)
- tol  = max(rtol*maximum(SVD.S), atol)
+ tol2 = max(rtol*maximum(SVD.S), atol)
  Stype = eltype(SVD.S)
  Sinv = fill!(similar(A, Stype, length(SVD.S)), 0)
- index = SVD.S .> tol
+ index = SVD.S .> tol2
  Sinv[index] .= pinv.(view(SVD.S, index))
  return SVD.Vt' * (Diagonal(Sinv) * SVD.U')
 end