ci: ensure that dependencies are being properly kept up to date

[XavierChanth]

- What I did

• Removed the dependency overrides from sshnoports
• Added --enforce-lockfile flag to pub gets in the multibuild
• This will now allow us to use pubspec.lock in sshnoports to achieve repeatable builds, instead of relying on pinned dependencies which dart doesn't have a good way of automatically updating.

- How I did it

- How to verify it

https://github.com/atsign-foundation/noports/actions/runs/8208067643

- Description for the changelog
ci: ensure that dependencies are being properly kept up to date