gh-119132: Remove "experimental" tag from the CPython free-threading. (gh-135550)

* gh-119132: Remove "experimental" tag from the CPython free-threading build

* Address code review

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

* Add NEWS.d

* Regen configure.ac

* Update doc

* Update

* Update

* Update

* Update Doc/howto/free-threading-python.rst

Co-authored-by: Peter Bierma <zintensitydev@gmail.com>

* Update ctypes.rst

* Update

* Update Doc/howto/free-threading-python.rst

Co-authored-by: T. Wouters <thomas@python.org>

* Apply suggestions from code review

Co-authored-by: T. Wouters <thomas@python.org>
Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

---------

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>
Co-authored-by: Peter Bierma <zintensitydev@gmail.com>
Co-authored-by: T. Wouters <thomas@python.org>

configure

@@ -1826,8 +1826,8 @@ Optional Features:
                           no)
   --enable-profiling      enable C-level code profiling with gprof (default is
                           no)
-  --disable-gil           enable experimental support for running without the
-                          GIL (default is no)
+  --disable-gil           enable support for running without the GIL (default
+                          is no)
   --enable-pystats        enable internal statistics gathering (default is no)
   --enable-optimizations  enable expensive, stable optimizations (PGO, etc.)
                           (default is no)