docs(notification_channel.html.markdown): fix import example

[leonardo-pizarro]

Description

Currently the notification_channel import example uses the notification_destination resource, which can lead to errors by the reader. This PR updates the example to match the notification_channel expected import

Type of change

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• This change requires a documentation update

Checklist:

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• My commit message follows conventional commits
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation

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