Resolve 'EntitySystem.Get<T>()' is obsolete in content (#27936)

* PROJECT 0 WARNINGS: Resolve `'EntitySystem.Get<T>()' is obsolete` in content

* pass entman

* dog ass test

* webeditor

Content.Server/Atmos/Components/AtmosPlaqueComponent.cs

@@ -14,7 +14,7 @@ namespace Content.Server.Atmos.Components
             set
             {
                 Type = value;
-                EntitySystem.Get<AtmosPlaqueSystem>().UpdateSign(Owner, this);
+                IoCManager.Resolve<IEntityManager>().System<AtmosPlaqueSystem>().UpdateSign(Owner, this);
             }
         }
     }