Refreshing local storage does not see json updates

[michael-s-crouch]

Describe the bug
When refreshing local storage, it doesn't load fields that have been added to existing .json files describing tasks.

To Reproduce
Import tasks from local storage using JSON-defined tasks. Then edit an existing JSON file, and re-sync the import.

Environment (please complete the following information):
Windows 10 Enterprise, Labelstudio v1.10.1dev

Additional context
I'm working on improving our labeling workflow by adding more context information, but I don't want to lose the many hours of manual labeling we already have.