Bump `arkindex-base-worker` to `0.3.7rc3`

The extraction is currently broken: https://demo.arkindex.org/process/0470f868-eef1-47bf-b03d-eb1480255452/0

.arkindex.yml

 ---
 version: 2
 
-type: worker
-
 workers:
   - slug: generic-training-dataset
     name: Generic Training Dataset Extractor