Fix exception when observer tries to take over GhostTakeoverAvailable mob that has a mind.

That method is essentially a `TryTake` method, why would it throw instead of returning false...

Content.Server/Ghost/Roles/Components/GhostTakeoverAvailableComponent.cs

@@ -25,7 +25,7 @@ namespace Content.Server.Ghost.Roles.Components
             var mind = Owner.EnsureComponent<MindComponent>();
 
             if (mind.HasMind)
-                throw new Exception("MindComponent already has a mind!");
+                return false;
 
             var sessionMind = session.ContentData()?.Mind;