chore(deps-py): update pydantic requirement in /hugr-py

Updates the requirements on [pydantic](https://github.com/pydantic/pydantic) to permit the latest version.
- [Release notes](https://github.com/pydantic/pydantic/releases)
- [Changelog](https://github.com/pydantic/pydantic/blob/main/HISTORY.md)
- [Commits](pydantic/pydantic@v2.7.0...v2.8.0)

---
updated-dependencies:
- dependency-name: pydantic
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

hugr-py/pyproject.toml

@@ -25,7 +25,7 @@ repository = "https://github.com/CQCL/hugr"
 
 [tool.poetry.dependencies]
 python = ">=3.10"
-pydantic = "~2.7.0"
+pydantic = ">=2.7,<2.9"
 
 [tool.pytest.ini_options]
 # Lark throws deprecation warnings for `src_parse` and `src_constants`.