gh-117739: Update definition of global interpreter lock for 3.13 (#117740)

Co-authored-by: Hugo van Kemenade <[email protected]>

Author: savannahostrowski

Doc/glossary.rst

@@ -547,12 +547,12 @@ Glossary
       tasks such as compression or hashing.  Also, the GIL is always released
       when doing I/O.
 
-      Past efforts to create a "free-threaded" interpreter (one which locks
-      shared data at a much finer granularity) have not been successful
-      because performance suffered in the common single-processor case. It
-      is believed that overcoming this performance issue would make the
-      implementation much more complicated and therefore costlier to maintain.
-
+      As of Python 3.13, the GIL can be disabled using the :option:`--disable-gil`
+      build configuration. After building Python with this option, code must be
+      run with :option:`-X gil 0 <-X>` or after setting the :envvar:`PYTHON_GIL=0 <PYTHON_GIL>`
+      environment variable. This feature enables improved performance for
+      multi-threaded applications and makes it easier to use multi-core CPUs
+      efficiently. For more details, see :pep:`703`.
 
    hash-based pyc
       A bytecode cache file that uses the hash rather than the last-modified