fix: make ToFacetsAsync cancellation test deterministic

Cancel token immediately instead of after 5ms to eliminate race
condition on fast CI runners where mapping completes before cancellation.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: dkattan

test/Facet.Tests/UnitTests/Extensions/Mapping/AsyncMappingTests.cs

@@ -114,7 +114,7 @@ public async Task ToFacetsAsync_ShouldHandleCancellation()
             TestDataFactory.CreateUser("Test2", "User2")
         };
         var cts = new CancellationTokenSource();
-        cts.CancelAfter(TimeSpan.FromMilliseconds(5)); 
+        cts.Cancel();
 
         var act = () => users.ToFacetsAsync<UserDto, UserDtoAsyncMapper>(cts.Token);
         await act.Should().ThrowAsync<OperationCanceledException>();