Remove contract tests that do not test the python client and fix depe… (#273)

- remove the tests that tests the unstructured library instead of the
python client
- remove unstructured from the project's dependency list

Author: jiajun-unstructured

_test_contract/test_partition_via_api.py

@@ -24,7 +24,6 @@ python:
       pytest-mock: '>=3.14.0'
       pytest-xdist: ^3.5.0
       types-aiofiles: '>=24.1.0'
-      unstructured: '>= 0.17.2'
       uvloop: '>=0.20.0'
     main:
       aiofiles: '>=24.1.0'