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.Server/GameObjects/Components/Disposal/DisposalUnitComponent.cs

@@ -381,7 +381,7 @@ namespace Content.Server.GameObjects.Components.Disposal
                 return;
             }
 
-            if (!(obj.Message is UiButtonPressedMessage message))
+            if (obj.Message is not UiButtonPressedMessage message)
             {
                 return;
             }