Fix unread count issue in subscriptions.get route

[Parvezkhan0]

Proposed changes (including videos or screenshots)

Resolved the issue related to incorrect unread message counts in the subscriptions.get route. Adjusted the subscriptions.get, subscriptions.read, and subscriptions.unread routes for improved accuracy. Removed subscriptions.getOne route as it was not contributing to the correct behavior.

Issue(s)

Closes #23977

Steps to test or reproduce

1. Go to a channel with unread messages.
2. Check the unread message count using the /api/v1/subscriptions.get API.
3. Confirm that the unread count now reflects the correct number of unread messages.

Further comments

Tested locally to ensure the changes fix the issue and don't introduce new problems. Removed subscriptions.getOne route as it seemed unnecessary for the use case.

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Latest commit: d7180c3

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[Parvezkhan0]

@ggazzo I have added the changesets. I hope my PR is good now.

[KevLehman]

Thanks for contributing :)

I haven't checked your PR, but a suggestion: pls use the lint config from the project before pushing, so we can get on the PR only the changes that fix the issue, instead of unrelated prettier changes 🤗

Also, as a rule, don't remove endpoints. An endpoint removal needs to be evaluated and then changed on a Major release.