fix: add text/csv handling to the python sdk [RUDOLPH-90]

[Klaijan]

This PR fixes the error when text/csv is passed to the param as below by adding the handling for text/csv

req = operations.PartitionRequest(
    partition_parameters=shared.PartitionParameters(
        files=files,
        strategy="fast",
        output_format="text/csv",
    )
)

To test:
Pull this branch and test on the local version of python client. Follow the guide here.
Or you could also install the client locally by pip install -v -e . to refer to the local version of the client.

JIRA Ticket

[Coniferish]

Hey @Klaijan! Can you add this bug fix to the changelog? Austin created one just before leaving for us to track changes manually. We don't have any checks in CI for changes, so we'll just have to remember to do so for now.

[Klaijan]

Error occur when try with 1-page pdf.
For extra context, the result is returned. But error was also raised.
1.pdf

unstructured_client.models.errors.sdkerror.SDKError: Unexpected response received (code: 200, type: text/plain; charset=utf-8): Status 200```