Use mpi-extensions main Open MPI in CI #5077

Job	Run time
ci-scope	5s
pre-commit / pre-commit	2m 8s
pre-commit / link-check	17s
mac / clang-build (Release)	1m 55s
windows / msvc-build (Debug)	1m 48s
windows / msvc-build (Release)	1m 50s
mac / clang-build (Debug)	1m 46s
ubuntu / clang-build (ubuntu-26.04)	44s
ubuntu / gcc-build (ubuntu-26.04, Debug)	45s
ubuntu / gcc-build (ubuntu-26.04, Release)	39s
windows / clang-build	1m 41s
ubuntu / clang-sanitizer-build	-1s
ubuntu / clang-test-extended	-1s
ubuntu / clang-test	-1s
ubuntu / clang-sanitizer-test	-1s
ubuntu / clang-sanitizer-test-extended	0s
ubuntu / gcc-test	0s
ubuntu / gcc-test-extended	0s
ubuntu / gcc-build-codecov	-1s
windows / clang-test	1s
windows / clang-test-extended	1s
windows / msvc-test	1s
windows / msvc-test-extended	1s
mac / clang-test	1s
mac / clang-test-extended	1s
pages	-1s
perf	-1s
	13m 37s

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