Update requirements.txt

Author: rwood-97

requirements.txt

@@ -3,4 +3,4 @@ detectron2 @ git+https://github.com/facebookresearch/detectron2.git
 DeepSolo @ git+https://github.com/maps-as-data/DeepSolo.git
 DPText-DETR @ git+https://github.com/maps-as-data/DPText-DETR.git
 MapTextPipeline @ git+https://github.com/maps-as-data/MapTextPipeline.git
-piffle @ git+https://github.com/rwood-97/piffle.git
+piffle @ git+https://github.com/rwood-97/piffle.git@iiif_dataclasses