Fix sinks and toilets not draining (#33691)

* Fix AutoDrain

Per the system comments, AutoDrain is designed to automatically move
puddles into the drain (like a floor drain). Drains without AutoDrain
are still supposed to gradually empty the buffer, but not remove puddles
(like sinks and toilets).

However, a logic error in the original implementation causes drains with
AutoDrain set to false to simply not work. Hence sinks never emptied.

* Update documentation

Content.Server/Fluids/EntitySystems/DrainSystem.cs

@@ -134,13 +134,6 @@ public sealed class DrainSystem : SharedDrainSystem
             }
             drain.Accumulator -= drain.DrainFrequency;
 
-            // Disable ambient sound from emptying manually
-            if (!drain.AutoDrain)
-            {
-                _ambientSoundSystem.SetAmbience(uid, false);
-                continue;
-            }
-
             if (!managerQuery.TryGetComponent(uid, out var manager))
                 continue;
 
@@ -160,6 +153,8 @@ public sealed class DrainSystem : SharedDrainSystem
             // This will ensure that UnitsPerSecond is per second...
             var amount = drain.UnitsPerSecond * drain.DrainFrequency;
 
+            if (drain.AutoDrain)
+            {
                 _puddles.Clear();
                 _lookup.GetEntitiesInRange(Transform(uid).Coordinates, drain.Range, _puddles);
 
@@ -197,6 +192,7 @@ public sealed class DrainSystem : SharedDrainSystem
                         QueueDel(puddle);
                     }
                 }
+            }
 
             _solutionContainerSystem.UpdateChemicals(drain.Solution.Value);
         }

Content.Shared/Fluids/Components/DrainComponent.cs

@@ -27,8 +27,8 @@ public sealed partial class DrainComponent : Component
     public float Accumulator = 0f;
 
     /// <summary>
-    /// Does this drain automatically absorb surrouding puddles? Or is it a drain designed to empty
-    /// solutions in it manually? 
+    /// If true, automatically transfers solutions from nearby puddles and drains them. True for floor drains;
+    /// false for things like toilets and sinks.
     /// </summary>
     [DataField]
     public bool AutoDrain = true;