[ci] Sync test areas yaml file with test-pipeline (#30862)

Signed-off-by: Kevin H. Luu <khluu000@gmail.com>

.buildkite/test_areas/models_basic.yaml

@@ -9,6 +9,7 @@ steps:
   source_file_dependencies:
   - vllm/
   - tests/models/test_initialization.py
+  - tests/models/registry.py
   commands:
     # Run a subset of model initialization tests
     - pytest -v -s models/test_initialization.py::test_can_initialize_small_subset
@@ -20,6 +21,7 @@ steps:
   source_file_dependencies:
   - vllm/model_executor/models/
   - tests/models/test_initialization.py
+  - tests/models/registry.py
   commands:
     # Only when vLLM model source is modified - test initialization of a large
     # subset of supported models (the complement of the small subset in the above