This PR reverts `pytesseract` dependency to `unstructured.pytesseract`
fork due to the unavailability of some recent release versions of
`pytesseract` on PyPI.
This PR also addresses an issue encountered during the publication of
`unstructured==0.15.4` to PyPI. The error was due to the fact that PyPI
does not allow direct dependencies from Version Control System URLs like
GitHub in the `install_requires` or `extras_require` sections of the
`setup.py` file.