Add Python 3.13 to list of allowed Python versions (#11411)

## Summary

I believe we're already "Python 3.13-ready"? The main Ruff-impacting
change I see in https://docs.python.org/3.13/whatsnew/3.13.html is [PEP
696](https://peps.python.org/pep-0696/) which Jelle added in
https://github.com/astral-sh/ruff/pull/11120.

crates/ruff_workspace/src/configuration.rs

@@ -181,6 +181,7 @@ impl Configuration {
                 PythonVersion::Py310 => ruff_python_formatter::PythonVersion::Py310,
                 PythonVersion::Py311 => ruff_python_formatter::PythonVersion::Py311,
                 PythonVersion::Py312 => ruff_python_formatter::PythonVersion::Py312,
+                PythonVersion::Py313 => ruff_python_formatter::PythonVersion::Py313,
             },
             line_width: self
                 .line_length