Obsolete property in send email sample

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### This issue is for a: (mark with an `x`)
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- [ ] bug report -> please search issues before submitting
- [ ] feature request
- [x] documentation issue or request
- [ ] regression (a behavior that used to work and stopped in a new release)
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`poller.getOperationState().isStarted` was removed in a version of azure/communication-email as of the official Microsoft documentation points in favor of `poller.getOperationState().status !== "running"`. Reporting this here as the provided sample code still references this older property and may cause issues for developers who do not catch the notice in the documentation and rely solely on this sample.

Reference in MS docs: https://learn.microsoft.com/en-us/azure/communication-services/quickstarts/email/send-email?tabs=windows%2Cconnection-string%2Csend-email-and-get-status-async%2Casync-client&pivots=programming-language-javascript

Issue in sample code file: `send-email/send-email.js` Line 27

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Ouvrez send-email/send-email.js à la ligne 27 et comparez l’exemple avec la documentation Microsoft liée. Mettez à jour l’exemple afin qu’il utilise la propriété d’état actuelle du poller d’e-mails, puis vérifiez que la référence obsolète à isStarted a disparu et que l’exemple reflète toujours le flux documenté.

Rédigé par le modèle d'indexation à partir du texte de l'issue.