[BUG] Cannot use Nitsche interface method with rectangles

**Describe the bug**
Nitsche interface method produces an error with hex-only mesh: "ValueError: Circumradius only makes sense for affine simplex cells."

**To Reproduce**
MWE to reproduce behavior:

```
import festim as F
from dolfinx.mesh import create_unit_square, CellType
from mpi4py import MPI
import numpy as np

fenics_mesh = create_unit_square(
MPI.COMM_WORLD, 10, 10, cell_type=CellType.quadrilateral
)
festim_mesh = F.Mesh(fenics_mesh)

my_model = F.HydrogenTransportProblemDiscontinuous()

material_top = F.Material(D_0=1, E_D=0, K_S_0=2, E_K_S=0)
material_bottom = F.Material(D_0=2, E_D=0, K_S_0=3, E_K_S=0)

top_volume = F.VolumeSubdomain(
id=3, material=material_top, locator=lambda x: x[1] >= 0.5
)
bottom_volume = F.VolumeSubdomain(
id=4, material=material_bottom, locator=lambda x: x[1] <= 0.5
)

top_surface = F.SurfaceSubdomain(id=1, locator=lambda x: np.isclose(x[1], 1.0))
bottom_surface = F.SurfaceSubdomain(id=2, locator=lambda x: np.isclose(x[1], 0.0))

my_model.mesh = festim_mesh
my_model.subdomains = [top_surface, bottom_surface, top_volume, bottom_volume]

my_model.surface_to_volume = {
top_surface: top_volume,
bottom_surface: bottom_volume,
}

my_model.method_interface = F.InterfaceMethod.nitsche
my_model.interfaces = [F.Interface(5, (bottom_volume, top_volume), penalty_term=1000)]

H = F.Species("H")
my_model.species = [H]
H.subdomains = [top_volume, bottom_volume]

my_model.temperature = 400

my_model.boundary_conditions = [
F.FixedConcentrationBC(subdomain=top_surface, value=1.0, species=H),
F.FixedConcentrationBC(subdomain=bottom_surface, value=0.0, species=H),
]

my_model.settings = F.Settings(atol=1e-10, rtol=1e-10, transient=False)

my_model.initialise()
my_model.run()
```

**Expected behavior**
Expected the simulation to solve using nitsche interface method.