Change `latest` Python version to Python 3.14

[dylwil3]

To finalize our stabilization of support for Python 3.14, we should address this TODO:

ruff/crates/ruff_python_ast/src/python_version.rs

Lines 58 to 61 in 5cace28

	// TODO: change this to 314 when it is released
	pub const fn latest() -> Self {
	Self::PY313
	}

[MichaReiser]

Note: We have to wait until Python 3.14 is officially released. We might also want to time the next minor to be aligned with the 3.14 release.

[dylwil3]

Python 3.14 release dates are:

• Candidate 1: July 22 (tomorrow, as of this writing)
• Candidate 2: August 26
• Final: October 7

If we want to wait until the final release, then most likely we will have one or two minors between now and then. We can update the milestone target accordingly.