doc: update flux_reactor_create(3) flags #2521

Job	Run time
spelling	11s
Generate build matrix	10s
validate commits	0s
python linting	30s
bookworm - test-install	5m 52s
bookworm - 32 bit	5m 53s
noble - test-install	5m 50s
el9 - test-install	5m 52s
alpine - test-install	5m 51s
fedora40 - test-install	5m 50s
jammy - test-install	5m 51s
focal - py3.8	5m 50s
bookworm - gcc-12,content-s3,distcheck	5m 51s
fedora40 - clang-18	5m 51s
coverage	5m 49s
el8 - ascii	5m 51s
el8 - test-install	5m 51s
el8 - system,coverage	5m 48s
inception	5m 49s
flux-accounting check	4m 39s
flux-pmix check	5m 29s
macos build only	3m 33s
flux-pam check	1m 51s
flux-sched check	5m 28s
Generate docker manifest	1s
	1h 49m 31s

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