Revert "Solution Entities" (#23160)

Revert "Solution Entities (#21916)"

This reverts commit d75e743dd7.

Content.Shared/Fluids/Components/DrainComponent.cs

@@ -1,4 +1,3 @@
-using Content.Shared.Chemistry.Components;
 using Content.Shared.Tag;
 using Robust.Shared.Audio;
 
@@ -20,9 +19,6 @@ public sealed partial class DrainComponent : Component
     [ValidatePrototypeId<TagPrototype>]
     public const string PlungerTag = "Plunger";
 
-    [DataField]
-    public Entity<SolutionComponent>? Solution = null;
-
     [DataField("accumulator")]
     public float Accumulator = 0f;