Use poetry-core as build backend

Author: fabaff

Diff for: openapi_python_client/templates/pyproject.toml.jinja

@@ -19,8 +19,8 @@ attrs = ">=20.1.0,<22.0.0"
 python-dateutil = "^2.8.0"
 
 [build-system]
-requires = ["poetry>=1.0"]
-build-backend = "poetry.masonry.api"
+requires = ["poetry-core>=1.0.0"]
+build-backend = "poetry.core.masonry.api"
 
 {% endif %}
 [tool.black]