Doc Cleanup

[gonsie]

Fixes #3101 - man1 command titles are now lowercase.

Fixes #3106 - each section index page no longer shows sections (SYNOPSIS, DESCRIPTION, etc.) of the individual man pages.

[garlick]

LGTM! Thanks!

[codecov-commenter]

Codecov Report

Merging #3117 into master will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3117      +/-   ##
==========================================
- Coverage   81.15%   81.13%   -0.03%     
==========================================
  Files         286      286              
  Lines       44494    44494              
==========================================
- Hits        36108    36098      -10     
- Misses       8386     8396      +10     

Impacted Files	Coverage Δ
src/broker/state_machine.c	77.50% <0.00%> (-1.67%)	⬇️
src/common/libsubprocess/server.c	61.64% <0.00%> (-0.86%)	⬇️
src/modules/job-archive/job-archive.c	58.89% <0.00%> (-0.80%)	⬇️
src/modules/job-exec/exec.c	79.62% <0.00%> (-0.62%)	⬇️
src/broker/overlay.c	75.00% <0.00%> (-0.33%)	⬇️
src/broker/broker.c	74.11% <0.00%> (-0.11%)	⬇️
src/broker/module.c	75.39% <0.00%> (ø)