examples: Update MPI notebook to reference inner and outer halo terminology #6347

Job	Run time
pytest-ubuntu-py311-gcc11-noomp-base	28m 45s
pytest-ubuntu-py311-gcc11-noomp-adjoint	27m 47s
pytest-ubuntu-py38-gcc12-omp-base	29m 1s
pytest-ubuntu-py38-gcc12-omp-adjoint	27m 59s
pytest-ubuntu-py37-gcc7-omp-base	29m 43s
pytest-ubuntu-py37-gcc7-omp-adjoint	28m 59s
pytest-ubuntu-py310-gcc10-noomp-base	27m 47s
pytest-ubuntu-py310-gcc10-noomp-adjoint	27m 22s
pytest-ubuntu-py312-gcc13-omp-base	41m 41s
pytest-ubuntu-py312-gcc13-omp-adjoint	39m 21s
pytest-ubuntu-py39-gcc9-omp-base	27m 48s
pytest-ubuntu-py39-gcc9-omp-adjoint	26m 49s
pytest-osx-py37-clang-omp-base	6m 14s
pytest-docker-py39-gcc-omp-base	30m 0s
pytest-docker-py39-gcc-omp-adjoint	25m 52s
pytest-docker-py39-icx-omp-base	24m 40s
pytest-docker-py39-icx-omp-adjoint	26m 41s
	7h 56m 29s

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