Reduce exported functions

[ohno]

It is not necessary to export orthogonal polynomials and other functions other than V, E and ψ.

- export HydrogenAtom, V, E, ψ, R, L, Y, P
+ export HydrogenAtom, V, E, ψ

[ohno]

The documentation and test codes should also be updated at the same time.

Antique.jl/docs/src/HydrogenAtom.md

Line 162 in 1084037

r -> r^2 * R(H,r,n=n,l=l)^2,

- r -> r^2 * R(H,r,n=n,l=l)^2,
+ r -> r^2 * Antique.R(H,r,n=n,l=l)^2,