CmdPal: Fix race condition in SupersedingAsyncGate cancellation handling [MSH] (#40983)

## Summary of the Pull Request

Change SetCanceled to TrySetCanceled in OperationCanceledException
handler to prevent InvalidOperationException when external and internal
cancellation tokens complete the TaskCompletionSource simultaneously.


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## PR Checklist

- [x] Closes: #40982
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** none
- [ ] **Localization:** nope
- [ ] **Dev docs:** none
- [ ] **New binaries:** none
- [ ] **Documentation updated:** none

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## Detailed Description of the Pull Request / Additional comments

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## Validation Steps Performed

src/modules/cmdpal/Microsoft.CmdPal.Common/Helpers/SupersedingAsyncGate.cs

@@ -89,7 +89,7 @@ public class SupersedingAsyncGate : IDisposable
                 }
                 catch (OperationCanceledException)
                 {
-                    CompleteIfCurrent(currentTcs, currentCallId, tcs => tcs.SetCanceled(currentCts.Token));
+                    CompleteIfCurrent(currentTcs, currentCallId, tcs => tcs.TrySetCanceled(currentCts.Token));
                 }
                 catch (Exception ex)
                 {