gh-152548: Fix the NEWS reference to the renamed isolated() decorator

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: serhiy-storchaka

Misc/NEWS.d/next/Tests/2026-06-29-10-14-09.gh-issue-152548.Khw9J7.rst

@@ -1,3 +1,3 @@
-Add the :func:`test.support.isolated` decorator to run a test method or
+Add the :func:`test.support.isolation.isolated` decorator to run a test method or
 ``TestCase`` subclass in a fresh interpreter subprocess, isolated from the rest
 of the test run.