Reduce USDC Credit limit on SNX-USDC to $100,000

The pool currently has $445K USDC credit available and a $500,000 credit limit which would profit users and veEXTRA holders more if it were reallocated to other higher profit pools.

There is only $93.3K TVL in the pool due to low returns and poor market perception of SNX prospects.

A lower credit limit will increase USDC utilization if the freed credit is reallocated to higher demand pools which will increase USDC rates, attract more deposits and increase profit potential for all users.