[ARFC] Sunset the Aptos Bug Bounty program and Cantina as a provider

An ARFC proposal by Aave Labs seeks to sunset the Aave V3 on Aptos bug bounty program on Cantina and remove Cantina as an active bug bounty provider, following the DAO's wind-down of the Aave V3 Aptos deployment due to sustained declines in liquidity and protocol revenue. With Aptos reserves (USDT, APT, USDC, sUSDe) frozen to new activity, the residual risk surface no longer supports a dedicated DAO-funded program, and Aave V3 on Aptos was Cantina's sole allocated scope under the bug bounty restructuring. Immunefi and Sherlock would remain the DAO's active bug bounty platforms, covering Core Aave V3/V2, GHO, non-liquidity infrastructure, Aave V4, and the Aave App Stack.