gh-145568: rename NEWS entry and expand description

Replace placeholder gh-issue-NNNNN with the real issue number 145568.
Expand the NEWS text to cover all 7 areas fixed by the parent commit
(struct-field races, child-list mutations, property getters/setters,
__copy__, __deepcopy__, TreeBuilder end-tag handling, and the
borrowed-reference fix in the expat entity handler).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Sebcio03

Misc/NEWS.d/next/Library/2026-03-05-17-45-00.gh-issue-145568.1LHFaD2C.rst

@@ -0,0 +1,12 @@
+Fix multiple data races in :mod:`xml.etree.ElementTree` for the free-threaded
+build.  Add :c:macro:`Py_BEGIN_CRITICAL_SECTION` guards and ``_lock_held``
+split-function patterns throughout ``Modules/_elementtree.c`` to protect
+:class:`~xml.etree.ElementTree.Element` struct fields, child-list mutations
+(:meth:`~xml.etree.ElementTree.Element.append`,
+:meth:`~xml.etree.ElementTree.Element.insert`,
+:meth:`~xml.etree.ElementTree.Element.clear`), property
+getters/setters, :meth:`~xml.etree.ElementTree.Element.__copy__`,
+:meth:`~xml.etree.ElementTree.Element.__deepcopy__`, and
+:class:`~xml.etree.ElementTree.TreeBuilder` end-tag handling.
+Also replace a :c:func:`PyDict_GetItemWithError` borrowed-reference lookup
+in the expat entity handler with :c:func:`PyDict_GetItemRef`.