Update Free-threaded single thread peformance section (still refer to 3.14 perf in future)

[Carreau]

Documentation

In https://docs.python.org/3.15/howto/free-threading-python.html#single-threaded-performance ,

cpython/Doc/howto/free-threading-python.rst

Lines 145 to 157 in ad0a3f7

	Single-threaded performance
	---------------------------
	The free-threaded build has additional overhead when executing Python code
	compared to the default GIL-enabled build. In 3.13, this overhead is about
	40% on the `pyperformance <https://pyperformance.readthedocs.io/>`_ suite.
	Programs that spend most of their time in C extensions or I/O will see
	less of an impact. The largest impact is because the specializing adaptive
	interpreter (:pep:`659`) is disabled in the free-threaded build. We expect
	to re-enable it in a thread-safe way in the 3.14 release. This overhead is
	expected to be reduced in upcoming Python release. We are aiming for an
	overhead of 10% or less on the pyperformance suite compared to the default
	GIL-enabled build.

This still refers to Python 3.14 as a future version of Python, and state that the perf impact is ~40%, plus that the adaptive interpreter has not been re-enabled.

I believe the adaptive interpreter is reenabled, the per impact are more in the ~5-10%, and 3.14 has been release.

If someone has already ran the pyperf benchmark and has a link to it for 3.14/3.14t, it would be great.

[Carreau]

Sorry, I don't know how I missed this other issue.