Fix sympy test

This test was failin localy with

    Expression: SymPy.simplify(symbolics_to_sympy(Symbolics.solve_for(expr, p))) == (SymPy.solve(sexpr, sp))[1]
     Evaluated: -2*t*(x^2 + y(t) - 1)/(x^2 + x + y(t) - 1) == 2*t*(-x^2 - y(t) + 1)/(x^2 + x + y(t) - 1)

While equal, they are not the same expression. `SymPy.simplify` and
`SymPy.solve` don't seem to guarantee identical expressions, so pass
both results through `simplify` to ensure they are comparable.

test/sympy.jl

@@ -21,4 +21,4 @@ expr = x * p + (x^2 - 1 + y) * (p + 2t)
 sexpr = symbolics_to_sympy(expr)
 sp = symbolics_to_sympy(p)
 
-@test SymPy.simplify(symbolics_to_sympy(Symbolics.solve_for(expr, p))) == SymPy.solve(sexpr, sp)[1]
+@test SymPy.simplify(symbolics_to_sympy(Symbolics.solve_for(expr, p))) == SymPy.simplify(SymPy.solve(sexpr, sp)[1])