Merge pull request #2332 from 0xProject/fix/staking/paramDocsForRewardsPaidOutEvent

Updated `RewardsPaid` event docs

contracts/staking/contracts/src/interfaces/IStakingEvents.sol

@@ -76,7 +76,7 @@ interface IStakingEvents {
     );
 
     /// @dev Emitted by MixinFinalizer when rewards are paid out to a pool.
-    /// @param epoch The epoch when the rewards were earned.
+    /// @param epoch The epoch when the rewards were paid out.
     /// @param poolId The pool's ID.
     /// @param operatorReward Amount of reward paid to pool operator.
     /// @param membersReward Amount of reward paid to pool members.