bug/wong-example-file-path-in-readme: Get "No such file or directory" error by following the steps in Readme

[shaofengshi]

Describe the bug
I follow the readme to run the example in docker container, but encountered a "No such file or directory." error.

To Reproduce
Just follow the steps in README.md:

python3

>>> from unstructured.partition.pdf import partition_pdf
>>> elements = partition_pdf(filename="example-docs/layout-parser-paper-fast.pdf")

Expected behavior
No error be reported.

Screenshots

Environment Info
This is from the latest docker image(downloads.unstructured.io/unstructured-io/unstructured:latest), not my local env. The bug is a document bug, not related with code.

Additional context
No; You just try it will know.

[shaofengshi]

I created a PR for this, please take a review: #3714