Remove stale test_results snapshot

The committed test_results was a pre-pdfplumber validation run: v0.1
extracted json using the old posterContent key, scored against reference
annotations that have since been updated, with pdfalto listed as the text
source. That output belongs to the poster2json-validation harness rather
than this repo. Drop the directory and its README tree entry; regenerate
with pdfplumber in the validation repo when needed.

Author: jimnoneill

README.md

@@ -134,8 +134,7 @@ posters-science-extraction-api/
 ├── Dockerfile               # Container build
 ├── docker-compose-prod.yml  # Docker orchestration
 ├── docs/                    # Documentation
-├── example_posters/         # Sample poster files
-└── test_results/            # Validation outputs
+└── example_posters/         # Sample poster files
 ```
 
 Poster text extraction and JSON structuring are provided by the