Remove code for synthetic data generation from Manager/OCR file

We should remove all code for synthetic data generation below this line https://gitlab.com/teklia/atr/dan/-/blob/66f0f92db68d23c1312c617c8556169b5423e18c/dan/manager/ocr.py#L678

changed milestone to %DAN-P2: Clean code and remove unused code

added P2 label

assigned to @schneider-y

You can nuke (@babadie approved)

mentioned in merge request !142 (merged)

closed