Fix isClaimed in api.derive.staking.{query, queryMulti}

Author: TarikGul

packages/api-derive/src/staking/stakerRewards.ts

@@ -153,7 +153,7 @@ function filterRewards (eras: EraIndex[], valInfo: [string, DeriveStakingQuery][
     .filter(({ validators }) => Object.keys(validators).length !== 0)
     .map((reward) =>
       objectSpread({}, reward, {
-        isClaimed: filter.some((f) => reward.era.eq(f)),
+        isClaimed: reward.isClaimed,
         nominators: reward.nominating.filter((n) => reward.validators[n.validatorId])
       })
     );