Fix MC-88371 crash

[rvbsm]

Starting from 1.21.2 (24w39a) DragonLandingPhase#doServerTick uses ServerLevel. Fixes #376

DragonLandingPhase#doServerTick

  @Override
- public void doServerTick() {
+ public void doServerTick(ServerLevel serverLevel) {
      if (this.targetLocation == null) {
          this.targetLocation = Vec3.atBottomCenterOf(
-             this.dragon.level().getHeightmapPos(Heightmap.Types.MOTION_BLOCKING_NO_LEAVES, EndPodiumFeature.getLocation(this.dragon.getFightOrigin()))
+             serverLevel.getHeightmapPos(Heightmap.Types.MOTION_BLOCKING_NO_LEAVES, EndPodiumFeature.getLocation(this.dragon.getFightOrigin()))
          );
      }
    ...
  }

[Riflusso]

@isXander can you merge it, please? 🥺 Or implement it by yourself🙏