SIP 28 Update collector address in vote escrow

If users unbond their veSGT tokens, a percentage of the SLP tokens are currently burnt.

I propose changing the collector address to the Sharedstake multisig treasury. This allows us to take steps towards protocol owned liquidity and raise funding for DAO costs and insurance.

The same 30% would be deducted on unstake, but instead of being burnt it will be sent to the multisig.