ci: pin torch/transformers in export-fixture (transformers 5.15 tracing regression)

Author: Ronald Tse

.github/workflows/test.yml

@@ -52,6 +52,7 @@ jobs:
         with: { python-version: "3.11" }
       - run: |
           python -m pip install --upgrade pip
+          pip install torch==2.12.1 transformers==5.14.1
           pip install -e ".[dev,train,export]"
       - name: IMF export + parity gate fixture tests (torch vs ORT)
         run: PYTHONPATH=src python -m pytest tests/test_imf_export.py tests/test_imf_parity.py -v