Update usages of ! is with is not (#2584)

* Update usages of ! is with is not

* Content.IntegrationTests commit

* Content.Server commit

* Content.Shared commit

Co-authored-by: Metal Gear Sloth <metalgearsloth@gmail.com>

Content.Client/GameObjects/Components/Observer/GhostComponent.cs

@@ -106,7 +106,7 @@ namespace Content.Client.GameObjects.Components.Observer
         {
             base.HandleComponentState(curState, nextState);
 
-            if (!(curState is GhostComponentState state)) return;
+            if (curState is not GhostComponentState state) return;
 
             CanReturnToBody = state.CanReturnToBody;