Add Al-Jazeera (English) investigations unit to legacy ruleset

[rocodes]

Status

Ready for review

Review Checklist

• [x] Changes to onboarded.txt are accurate
• [x] The file default.rulesets.TIMESTAMP.gz has been updated, extracting that file and inspecting the contents of the JSON file produces the expected rules
• [x] The ruleset has been verified by modifying the HTTPS Everywhere configuration in a Tor Browser instance pointing to Path Prefix: https://raw.githubusercontent.com/freedomofpress/securedrop-https-everywhere-ruleset/$BRANCH_NAME
• [x] index.html has been updated using ./update_index.sh

Post-Deployment Checklist

• [x] Added/modified onion names have been updated in the SecureDrop Directory

[zenmonkeykstop]

This should probably have key-rotation-2021 as a base instead - IIRC that's the branch used to update the new channel