Reduce BUSD Borrow Cap

Our team has been monitoring BUSD liquidity in DEX since minting of BUSD was paused.

Recently, BUSD liquidity in PancakeSwap V2 has been shrinking rapidly with no sign of bouncing back: 220.30M on May 20th to 153.69M on May 31st.

We would like to propose to Venus protocol to reduce its borrow cap of BUSD from 130M to 80M. The change may not have immediate impact on the protocol as its current supply is ~60M and current borrow is ~50M, however it will help protocol to mitigate risk under unexpected scenarios.