Update news entry

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
0bbf3a8344a8ed0bbad230bca7f41bca45da23fc
commit 0bbf3a8344a8ed0bbad230bca7f41bca45da23fc
diff --git a/Misc/NEWS.d/next/Library/2023-03-10-13-21-16.gh-issue-102578.-gujoI.rst b/Misc/NEWS.d/next/Library/2023-03-10-13-21-16.gh-issue-102578.-gujoI.rst
@@ -1,24 +1,4 @@
-Speed up sanity check for ``__setattr__`` and ``__delattr__`` for frozen
-``dataclass``\es by using ``set``-based name lookup rather than ``tuple``\s.
-
-The sanity check is always performed, even if the ``dataclass`` is inherited.
-For example:
-
-.. code-block:: python
-
-    @dataclass(frozen=True)
-    class FrozenBase:
-        x: int
-        y: int
-        ... # N_FIELDS
-
-    class Foo(FrozenBase):
-        def __init__(self, x, y, somevalue, someothervalue):
-            super().__init__(x, y)
-            self.somevalue = somevalue            # takes O(N_FIELDS)
-            self.someothervalue = someothervalue  # takes O(N_FIELDS) time again
-
-    foo = Foo(1, 2, 3, 4)
-    foo.extravalue = extravalue  # takes O(N_FIELDS) time again
-
-This change makes the sanity check :math:`O(1)` in the number of fields.
+Speed up setting or deleting mutable attributes on non-dataclass subclasses of
+frozen dataclasses. Due to the implementation of ``__setattr__`` and
+``__delattr__`` for frozen dataclasses, this previously had a time complexity
+of ``O(n)``. It now has a time complexity of ``O(1)``.