system_tables.md: update _pico_privilege

Summary

• system_tables.md: update _pico_privilege

Address changes from picodata@e6d0f4b1

picodata 24.6.0-51-ge6d0f4b1

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• Close #341 (closed)
• Cherry-pick to: none
• Staging: https://docs.binary.picodata.io/picodata/asabirov_update_pico_privilege/architecture/system_tables/#_pico_privilege