Hi.

How do I export the results of mixed formulation with fenics-dolfinx v0.8.0?

The essence of my code is :

```
mesh = dolfinx.mesh.create_rectangle(MPI_COMM_WORLD,
np.array([[0.0, 0.0], [width, height]]),
[nx, ny],
cell_type=dolfinx.mesh.CellType.quadrilateral)
Q2 = basix.ufl.element("CG", mesh.basix_cell(), 2, shape=(mesh.geometry.dim,), dtype=dolfinx.default_real_type)
Q1 = basix.ufl.element("CG", mesh.basix_cell(), 1, dtype=dolfinx.default_real_type)
MixedSpace = dolfinx.fem.functionspace(mesh,basix.ufl.mixed_element([Q2,Q1]))
V, dofV = MixedSpace.sub(0).collapse()
Q, dofQ = MixedSpace.sub(1).collapse()
# X={U,P} : solution of the problem
X = dolfinx.fem.Function(MixedSpace)
solver.solve(X)
U = dolfinx.fem.Function(V)
U.x.array[:] = X.x.array[dofV]
P = dolfinx.fem.Function(Q)
P.x.array[:] = X.x.array[dofQ]
ofile = dolfinx.io.XDMFFile(mesh.comm,"result.xdmf","w")
ofile.write_mesh(mesh)
ofile.write_function(U)
ofile.write_function(P)
```

and this code causes error like :

Degree of output Function must be same as mesh degree. Maybe the Function needs to be interpolated?

Thank you.