Update website to reflect Muti-Mind hero retirement

[jflowers]

Summary

Muti-Mind (Product Owner) is being retired as a hero persona (see unbound-force/unbound-force#565). The website needs to be updated to reflect this change.

Work Required

• Remove Muti-Mind from the hero roster on the homepage and any hero/agent documentation pages
• Update any references to "five heroes" to reflect the new count
• Update the intake/requirements section to reference intake-kit as the intake layer (replacing Muti-Mind's role)
• Review blog posts for stale Muti-Mind references (informational context is fine; claiming Muti-Mind is active is not)

Context

intake-kit + the complytime RFC workflow replace Muti-Mind's strategically valuable capabilities. See unbound-force/unbound-force#565 for full rationale.