Increase USDC credit limit on USDC-AERO pool to 20mm

The Aero-USDbC pool is effectively deprecated but has about $2.4mm TVL on it, about 80% of the total pool on Aerodrome. This pool generates little in the way of fees and LP rewards and should be sunset on Extra.

The remaining LPs on the USDbC pool want to unwind (being unable to generate much APR) but aren't going to be able to maintain their positioning without enough capacity on the USDC pool (which is currently maxed and has been for months).

Replicating the borrow capacity on the USDbC pool and applying it to the USDC pool would allow for an easy transition and functional sunsetting of USDbC, which is something that is good for the ecosystem and LPs as we broadly move onto native USDC.

In the meantime, Aero has by far the most liquidity on this platform and has been constrained by USDC capacity for months. Increasing the USDC credit limit of the dex's central token to 20mm would provide enough headroom for continued IVL growth and hasten the move away from USDC.E.