build: pin python-docx (#3110)
Since we incorporate a newer feature from `python-docx`
[here](https://github.com/Unstructured-IO/unstructured/blob/main/unstructured/partition/docx.py#L521),
we should make the version of `python-docx` that first supports that
method an explicit requirement.
I didn't pip recompile since our generated dependencies already have
`python-docx==1.1.2`, but I can do that if someone thinks it's
necessary.
