Update metadata to use PEP 621 (#654)

* Drop python version 3.8 support
* Add python 3.13 support in CI

tests/test_version.py

@@ -12,5 +12,5 @@ def test_version():
     with PROJECT_TOML.open() as toml_file:
         project_config = tomlkit.loads(toml_file.read())
     assert (
-        __version__ == project_config["tool"]["poetry"]["version"]
+        __version__ == project_config["project"]["version"]
     ), "Project version should match in package and package config"