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.Shared/GameObjects/Components/SharedStackComponent.cs

@@ -97,7 +97,7 @@ namespace Content.Shared.GameObjects.Components
 
         public override void HandleComponentState(ComponentState curState, ComponentState nextState)
         {
-            if (!(curState is StackComponentState cast))
+            if (curState is not StackComponentState cast)
             {
                 return;
             }