fix: keep the update channel from being cleaned up

[eNdiD]

• add counter in Notifier for every machineKey
• do not remove channel if counter is more than 1

• [x] read the CONTRIBUTING guidelines
• [x] raised a GitHub issue or discussed it on the projects chat beforehand
• [ ] added unit tests
• [ ] added integration tests
• [ ] updated documentation if needed
• [ ] updated CHANGELOG.md

Fixes #1798