Fix conversion_type for NormalizedPolynomialSpace

[jishnub]

After this,

julia> conversion_type(NormalizedLegendre(), Jacobi(1,1))
NormalizedLegendre()

julia> conversion_type(NormalizedJacobi(2,2), Jacobi(1,1))
Jacobi(1,1)

[codecov]

Codecov Report

Patch coverage: 86.56% and project coverage change: +1.14 🎉

Comparison is base (69c583a) 69.14% compared to head (581a539) 70.28%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #243      +/-   ##
==========================================
+ Coverage   69.14%   70.28%   +1.14%     
==========================================
  Files          28       28              
  Lines        2573     2625      +52     
==========================================
+ Hits         1779     1845      +66     
+ Misses        794      780      -14     

Impacted Files	Coverage Δ
src/ApproxFunOrthogonalPolynomials.jl	81.48% <ø> (ø)
src/Spaces/Jacobi/jacobitransform.jl	100.00% <ø> (ø)
src/Spaces/Ultraspherical/DirichletSpace.jl	50.45% <37.93%> (+0.45%)	⬆️
src/Spaces/Chebyshev/Chebyshev.jl	59.85% <100.00%> (ø)
src/Spaces/Chebyshev/ChebyshevOperators.jl	97.14% <100.00%> (+10.28%)	⬆️
src/Spaces/Jacobi/Jacobi.jl	66.66% <100.00%> (+0.32%)	⬆️
src/Spaces/Jacobi/JacobiOperators.jl	83.50% <100.00%> (-0.18%)	⬇️
src/Spaces/PolynomialSpace.jl	92.90% <100.00%> (+0.95%)	⬆️
src/Spaces/Spaces.jl	100.00% <100.00%> (ø)
src/Spaces/Ultraspherical/Ultraspherical.jl	93.10% <100.00%> (+2.03%)	⬆️
... and 1 more

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