Limit pydantic to v1 (#474)

It appears v2 has breaking changes which we need to adjust for later.

Author: shsms

pyproject.toml

@@ -30,7 +30,7 @@ dependencies = [
   "networkx >= 2.8, < 4",
   "numpy >= 1.24.2, < 2",
   "protobuf >= 4.21.6, < 5",
-  "pydantic >= 1.9",
+  "pydantic >= 1.9, < 2",
   "toml >= 0.10",
   "tqdm >= 4.38.0, < 5",
   "typing_extensions >= 4.4.0, < 5",