fix: Prepares for IPooledEnumerable removal (#1548)

### Summary

- Removes `IPooledEnumerable` (non-generic)
- Changes `IPooledEnumerable<T>` so that  `Free()` is replaced with the `IDisposable` pattern

Projects/UOContent/Spells/Seventh/ChainLightning.cs

@@ -56,8 +56,6 @@ namespace Server.Spells.Seventh
                         pool.Enqueue(m);
                     }
 
-                    eable.Free();
-
                     if (pool.Count > 0)
                     {
                         double damage = Core.AOS

Projects/UOContent/Spells/Seventh/MassDispel.cs

@@ -69,8 +69,6 @@ namespace Server.Spells.Seventh
                         }
                     }
 
-                    eable.Free();
-
                     while (queue.Count > 0)
                     {
                         queue.Dequeue().Delete();

Projects/UOContent/Spells/Seventh/MeteorSwarm.cs

@@ -60,8 +60,6 @@ namespace Server.Spells.Seventh
                         queue.Enqueue(m);
                     }
 
-                    eable.Free();
-
                     double damage = Core.AOS
                         ? GetNewAosDamage(51, 1, 5, playerVsPlayer)
                         : Utility.Random(27, 22);