Re-enable the model generation test on Python 3.15 #1127

datamodel-code-generator fails to import on Python 3.15 ('3.15' is not a valid PythonVersion, raised from datamodel_code_generator/model/__init__.py), so #1122 skips test_model_generation_pipeline on 3.15. The fix is upstream in datamodel-code-generator/datamodel-code-generator#4609.

Once a datamodel-code-generator release supports Python 3.15, bump it and remove the skipif from test_model_generation_pipeline in tests/unit/test_model_generation.py.

✍️ Drafted by Claude Code