Remove `mumps-avoid-mpi-in-place` restriction on MacOS once MUMPS bug is fixed.

[JHopeCollins]

MUMPS has a bug on macOS that causes segfaults when it uses MPI_IN_PLACE. The mumps-avoid-mpi-in-place flag has been added to the macOS firedrake-configure output to avoid this for now, but should be removed once the bug is fixed.

Firedrake issue: #4102
Conda feedstock issue with fix: conda-forge/mumps-feedstock#110 (the title says OpenMPI only but there is a comment further down saying it affects MPICH too).

Relevant lines in firedrake-configure:

firedrake/scripts/firedrake-configure

Lines 372 to 374 in 10100ba

	# Avoid macos + openmpi + mumps segmentation violation issue;
	# see https://github.com/firedrakeproject/firedrake/issues/4102.
	configure_options.append("-download-mumps-avoid-mpi-in-place")