Resolve soft dependency on ocrmypdf

[krmax44]

We softly depend on ocrmypdf here:

django-filingcabinet/src/filingcabinet/pdf_utils.py

Line 368 in d27b0a8

def run_ocr(filename, language=None, binary_name="ocrmypdf", timeout=50):

I suggest simply adding the Python package to the dependencies and directly using its API instead of a CLI workaround.