cgp-0233: clarify base fee authority and follow-up CGP scope

[pahor167]

Summary

• Specify that base fee setting authority is delegated to the Celo Core Co. 6/8 multisig (0x9Eb44Da23433b5cAA1c87e35594D15FcEb08D34d)
• Update the follow-up CGP table to only list components that require separate onchain CGPs (burn + Carbon Offset Fund pause)

Test plan

• Verify rendered markdown on GitHub
• Confirm multisig address is correct