Adjust Referral Program for lending/borrowing

Since Lido integrated with Aave (lending stETH to borrow ETH) it's proposed to extend Referral Program terms & conditions with a rule: "Staking of ETH borrowed on lending/borrowing protocols (like Aave and others) is not going to be rewarded. It also relates to ETH that was bought with any other borrowed cryptocurrency (like DAI).” Referrals will get reward for the initially staked ETH but not for the secondary staked borrowed ETH.

Motivation: to spend referral rewards pool most effectively

Full proposal is here