ci: exclude mpi diff tests #468

Job	Run time
Windows MSVC CMake REL TS	8m 58s
Windows MSVC CMake DBG TS	7m 47s
Windows MSVC CMake REL	18m 17s
Windows MSVC CMake DBG	18m 43s
Ubuntu gcc CMake REL TS	5m 6s
Ubuntu gcc CMake DBG TS	3m 48s
Ubuntu gcc CMake REL	7m 55s
Ubuntu gcc CMake DBG	8m 41s
Ubuntu gcc Autotools REL TS	7m 22s
Ubuntu gcc Autotools DBG TS	6m 3s
Ubuntu gcc Autotools REL	15m 56s
Ubuntu gcc Autotools DBG	20m 13s
Ubuntu gcc Autotools parallel (build only) REL TS	7m 27s
Ubuntu gcc Autotools parallel (build only) DBG TS	5m 26s
Ubuntu gcc Autotools parallel (build only) REL	7m 11s
Ubuntu gcc Autotools parallel (build only) DBG	6m 54s
MacOS Clang CMake REL TS	3m 19s
MacOS Clang CMake DBG TS	2m 16s
MacOS Clang CMake REL	7m 26s
MacOS Clang CMake DBG	8m 9s
Ubuntu gcc Autotools v1.6 default API (build only) DBG	12m 24s
Ubuntu gcc Autotools v1.8 default API (build only) DBG	9m 7s
Ubuntu gcc Autotools v1.10 default API (build only) DBG	9m 9s
Ubuntu gcc Autotools v1.12 default API (build only) DBG	10m 44s
Ubuntu gcc Autotools v1.14 default API (build only) DBG	12m 37s
Ubuntu gcc Autotools no deprecated symbols (build only) DBG	8m 56s
Ubuntu gcc Autotools -Werror (build only) DBG	7m 38s
Ubuntu gcc Autotools -Werror (build only) REL	7m 38s
Ubuntu gcc Autotools parallel -Werror (build only) DBG	6m 8s
Ubuntu gcc Autotools parallel -Werror (build only) REL	6m 22s
	4h 27m 40s

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