fix: coordinates metadata hinders chunking (#1374)
Closes https://github.com/Unstructured-IO/unstructured/issues/1373
This PR:
- drops the `coordinates` metadata field in `chunk_by_title` to fix
https://github.com/Unstructured-IO/unstructured/issues/1373 (read issue
for the details)
- adds relevant test that checks the particular case
