End-of-stable-life-cycle legacy archive for FF91

• version 91-1
• use this with ESR91

changes [diffs]

• security: 0307: systemAddon prefs made inactive and moved to 7014 in section "7000: DON'T BOTHER"
• security: 0706: network.proxy.failover_direct changed to inactive
• misc: grammar, typos, reference tweaks