Fix content.integration tests warnings (#17817)

Co-authored-by: metalgearsloth <31366439+metalgearsloth@users.noreply.github.com>

Content.IntegrationTests/Tests/Slipping/SlippingTest.cs

@@ -1,10 +1,8 @@
 #nullable enable
 using System.Collections.Generic;
-using System.Threading.Tasks;
 using Content.IntegrationTests.Tests.Interaction;
 using Content.Shared.Slippery;
 using Content.Shared.Stunnable;
-using NUnit.Framework;
 using Robust.Shared.GameObjects;
 using Robust.Shared.Input;
 using Robust.Shared.Maths;
@@ -34,20 +32,24 @@ public sealed class SlippingTest : MovementTest
         await SpawnTarget("TrashBananaPeel");
 
         // Player is to the left of the banana peel and has not slipped.
+#pragma warning disable NUnit2045
         Assert.That(Delta(), Is.GreaterThan(0.5f));
-        Assert.That(sys.Slipped.Contains(Player), Is.False);
+        Assert.That(sys.Slipped, Does.Not.Contain(Player));
+#pragma warning restore NUnit2045
 
         // Walking over the banana slowly does not trigger a slip.
         await SetKey(EngineKeyFunctions.Walk, BoundKeyState.Down);
         await Move(DirectionFlag.East, 1f);
+#pragma warning disable NUnit2045
         Assert.That(Delta(), Is.LessThan(0.5f));
-        Assert.That(sys.Slipped.Contains(Player), Is.False);
+        Assert.That(sys.Slipped, Does.Not.Contain(Player));
+#pragma warning restore NUnit2045
         AssertComp<KnockedDownComponent>(false, Player);
 
         // Moving at normal speeds does trigger a slip.
         await SetKey(EngineKeyFunctions.Walk, BoundKeyState.Up);
         await Move(DirectionFlag.West, 1f);
-        Assert.That(sys.Slipped.Contains(Player), Is.True);
+        Assert.That(sys.Slipped, Does.Contain(Player));
         AssertComp<KnockedDownComponent>(true, Player);
     }
 }