In progress fix

[saunderez]

Describe your changes

Removed stale references to in_progress from shared.py and train_dreambooth.py to fix issue 1346

Issue ticket number and link (if applicable)

https://github.com/d8ahazard/sd_dreambooth_extension/issues/1346

Checklist before requesting a review

• [ ] This is based on the /dev branch (Or a fork of it)
• [X] This was created or at least validated using a proper IDE
• [X] I have tested this code and validated any modified functions
• [ ] I have added the appropriate documentation and hint strings if adding or changing a user-facing feature