small fix to m_mpi_proxy.fpp #141

Job	Run time
Github \| Docker	58m 20s
Github (ubuntu, mpi, debug, true)	41m 11s
Github (ubuntu, mpi, debug, false)	38m 43s
Georgia Tech \| Phoenix (NVHPC) (cpu)	44m 41s
Github (ubuntu, mpi, no-debug, true)	49m 52s
Georgia Tech \| Phoenix (NVHPC) (gpu)	28m 40s
Github (ubuntu, mpi, no-debug, false)	58m 39s
Github (ubuntu, no-mpi, debug, true)	18m 3s
Github (ubuntu, no-mpi, debug, false)	20m 28s
Github (ubuntu, no-mpi, no-debug, true)	31m 32s
Github (ubuntu, no-mpi, no-debug, false)	19m 41s
Github (macos, mpi, debug, false)	1h 2m 48s
Github (macos, mpi, no-debug, false)	58m 6s
Github (macos, no-mpi, debug, false)	9m 55s
Github (macos, no-mpi, no-debug, false)	34m 6s
	9h 34m 45s

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