docs: remove duplication in changelog for 2.9.0

Author: henryiii

docs/changelog.rst

@@ -19,10 +19,6 @@ New Features:
   used.
   `#3402 <https://github.com/pybind/pybind11/pull/3402>`_
 
-* Add C++ Exception type to throw and catch ``AttributeError``. Useful for
-  defining custom ``__setattr__`` and ``__getattr__`` methods.
-  `#3387 <https://github.com/pybind/pybind11/pull/3387>`_
-
 Changes:
 
 * Make str/bytes/memoryview more interoperable with ``std::string_view``.
@@ -35,11 +31,6 @@ Changes:
 
 Bug fixes:
 
-* Fix a regression in 2.8.0 that caused undefined behavior (typically
-  segfaults) in ``make_key_iterator``/``make_value_iterator`` if dereferencing
-  the iterator returned a temporary value instead of a reference.
-  `#3348 <https://github.com/pybind/pybind11/pull/3348>`_
-
 * Fix a rare warning about extra copy in an Eigen constructor.
   `#3486 <https://github.com/pybind/pybind11/pull/3486>`_
 
@@ -53,25 +44,10 @@ Bug fixes:
   ``python dev`` label.
   `#3419 <https://github.com/pybind/pybind11/pull/3419>`_
 
-* Fix 2.8.0 regression with MSVC 2017 + C++17 mode + Python 3.
-  `#3407 <https://github.com/pybind/pybind11/pull/3407>`_
-
-* Modernize usage of ``PyCodeObject`` on Python 3.9 (toward supporting Python
-  3.11a1)
-  `#3368 <https://github.com/pybind/pybind11/pull/3368>`_
-
-* A long-standing bug in eigen.h was fixed (originally PR #3343). The bug was
-  unmasked by newly added ``static_assert``'s in the Eigen 3.4.0 release.
-  `#3352 <https://github.com/pybind/pybind11/pull/3352>`_
-
 * Replace usage of deprecated ``Eigen::MappedSparseMatrix`` with
   ``Eigen::Map<Eigen::SparseMatrix<...>>`` for Eigen 3.3+.
   `#3499 <https://github.com/pybind/pybind11/pull/3499>`_
 
-* Fixed the potential for dangling references when using properties with
-  ``std::optional`` types.
-  `#3376 <https://github.com/pybind/pybind11/pull/3376>`_
-
 * Tweaks to support Microsoft Visual Studio 2022.
   `#3497 <https://github.com/pybind/pybind11/pull/3497>`_
 
@@ -84,13 +60,6 @@ Build system improvements:
   space in the package status message.
   `#3472 <https://github.com/pybind/pybind11/pull/3472>`_
 
-* Support multiple raw inclusion of CMake helper files (Conan.io does this for
-  multi-config generators).
-  `#3420 <https://github.com/pybind/pybind11/pull/3420>`_
-
-* Fix harmless warning on CMake 3.22.
-  `#3368 <https://github.com/pybind/pybind11/pull/3368>`_
-
 * Flags starting with ``-g`` in ``$CFLAGS`` and ``$CPPFLAGS`` are no longer
   overridden by ``.Pybind11Extension``.
   `#3436 <https://github.com/pybind/pybind11/pull/3436>`_