Revert scheduler changes. #11818

Job	Run time
build_details	4s
build_opam (4.14.x)	9m 6s
build_js	2m 5s
build_opam (5.2.x)	5m 13s
build_no_depopts	5m 55s
tree_sitter_parse	49s
build_win32 (x64)	18m 1s
lezer_parse	54s
run_tests (@citest)	12m 46s
run_tests (@doctest)	7m 48s
build_posix (debian_trixie, amd64)	14m 53s
update_doc	0s
run_tests (@mediatest)	12m 36s
build_posix (debian_bookworm, amd64)	15m 3s
build_posix (ubuntu_oracular, amd64)	14m 44s
build_posix (ubuntu_noble, amd64)	14m 42s
build_posix (alpine, amd64)	12m 55s
fetch_s3_artifacts	20s
build_docker_alpine_minimal (amd64)	48s
build_docker (amd64)	2m 21s
build_docker_alpine (amd64)	56s
build_docker_minimal (amd64)	1m 59s
build_docker_release-minimal	0s
update_release	0s
build_docker_release	0s
	2h 33m 58s

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