fix: rename X218 for X128 (#356)

Co-authored-by: Sara Reynolds <[email protected]>

Author: abdulla-cb

test/shared/FeeMath.sol

@@ -35,11 +35,11 @@ library FeeMath {
         (uint128 liquidity, uint256 feeGrowthInside0LastX128, uint256 feeGrowthInside1LastX128) =
             manager.getPositionInfo(poolId, address(posm), config.tickLower, config.tickUpper, bytes32(tokenId));
 
-        (uint256 feeGrowthInside0X218, uint256 feeGrowthInside1X128) =
+        (uint256 feeGrowthInside0X128, uint256 feeGrowthInside1X128) =
             manager.getFeeGrowthInside(poolId, config.tickLower, config.tickUpper);
 
         feesOwed = getFeesOwed(
-            feeGrowthInside0X218, feeGrowthInside1X128, feeGrowthInside0LastX128, feeGrowthInside1LastX128, liquidity
+            feeGrowthInside0X128, feeGrowthInside1X128, feeGrowthInside0LastX128, feeGrowthInside1LastX128, liquidity
         );
     }