man1: improve HTML formatting of man pages #7746

Job	Run time
Generate build matrix	10s
validate commits	19s
python linting	1m 6s
spelling	8s
bookworm	22m 4s
bookworm - 32 bit	23m 40s
bookworm - gcc-12,content-s3,distcheck	29m 31s
bookworm - py3.11,clang-15	22m 51s
coverage	45m 38s
jammy - test-install	18m 42s
bookworm - test-install	19m 47s
focal - py3.8	23m 35s
el8	36m 49s
el8 - ascii	14m 3s
el8 - system,coverage	10m 50s
fedora34 - gcc-11.2,py3.9	31m 12s
fedora38 - gcc-13.1,py3.11	22m 5s
inception	25m 18s
flux-accounting check	6m 30s
flux-sched check	8m 59s
flux-pam check	6m 50s
flux-pmix check	22m 16s
Generate docker manifest	1s
	6h 32m 24s

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