Update the info in the Payout Strategy box

According to the[ last update related to the Grants Program Doc](https://github.com/decentraland/documentation/pull/393) that saids __"These contracts are initiated by the DAO Committee within **15 days of the grant’s approval** by the DAO and have a cliff period of 30 days counting from the finalization of the voting process. In addition, the vesting contract will begin on the 1st or 15th day after the grant is approved."_ The info in the Payout Strategy box should be changed from 7 to 15 days.