Fix regression introduced in #2337 for dolfinx.mesh.create_interval

[francesco-ballarin]

Hi,
I believe this was introduced yesterday in #2337.

pybind11 wrappers for dolfinx.mesh.create_mesh_partitioner with no input arguments have been removed,
compare
https://github.com/FEniCS/dolfinx/blame/main/python/dolfinx/wrappers/mesh.cpp#L369
to
https://github.com/FEniCS/dolfinx/blame/4a5d20a9577b73052667644611fc014cd17257c1/python/dolfinx/wrappers/mesh.cpp#L380

which on main, at least for my local installation, makes a simple code such as

import dolfinx.mesh
import mpi4py.MPI
dolfinx.mesh.create_interval(mpi4py.MPI.COMM_WORLD, 30, [1, 5])

fail with

Traceback (most recent call last):
  File "test.py", line 3, in <module>
    dolfinx.mesh.create_interval(mpi4py.MPI.COMM_WORLD, 30, [1, 5])
  File "dolfinx/mesh.py", line 324, in create_interval
    partitioner = _cpp.mesh.create_cell_partitioner()
TypeError: create_cell_partitioner(): incompatible function arguments. The following argument types are supported:
    1. (arg0: dolfinx.cpp.mesh.GhostMode) -> Callable[[MPICommWrapper, int, int, dolfinx::graph::AdjacencyList<long>], dolfinx::graph::AdjacencyList<int>]
    2. (part: Callable[[MPICommWrapper, int, dolfinx::graph::AdjacencyList<long>, bool], dolfinx::graph::AdjacencyList<int>]) -> Callable[[MPICommWrapper, int, int, dolfinx::graph::AdjacencyList<long>], dolfinx::graph::AdjacencyList<int>]

I am not sure why CI did not catch this. I cannot even reproduce on dolfinx/dolfinx:nightly docker image.

[chrisrichardson]

I must have missed this one. As you say, it should have been picked up by the CI. Why not?

[francesco-ballarin]

It seems that dolfinx.mesh.create_interval is not used at all in the unit tests. I have added a new commit using it once.