cast to Float64 directly instead of using float

[SobhanMP]

Does this make sense?

Closes #515

julia> using SparseArrays, ForwardDiff, LinearAlgebra
julia> A = ForwardDiff.Dual.(sprand(10, 10, 0.1));
julia> qr(A)
ERROR: MethodError: no method matching Float64(::ForwardDiff.Dual{Nothing, Float64, 0})
The type `Float64` exists, but no method is defined for this combination of argument types when trying to construct it.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 84.26%. Comparing base (a5e95ec) to head (0c8f8f3).

Files	Patch %	Lines
src/solvers/spqr.jl	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #521   +/-   ##
=======================================
  Coverage   84.26%   84.26%           
=======================================
  Files          12       12           
  Lines        9122     9122           
=======================================
  Hits         7687     7687           
  Misses       1435     1435           

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[rayegun]

What happens in the complex case?

[SobhanMP]

What happens in the complex case?

The same as it used to do.