Add set deprecation notice (#6056)

* add notice

Signed-off-by: Michael Carlstrom <[email protected]>

* fix backtick

Signed-off-by: Michael Carlstrom <[email protected]>

* Update source/Releases/Release-Lyrical-Luth.rst

Co-authored-by: Tomoya Fujita <[email protected]>
Signed-off-by: Michael Carlstrom <[email protected]>

* Update source/Releases/Release-Lyrical-Luth.rst

Co-authored-by: Tomoya Fujita <[email protected]>
Signed-off-by: Michael Carlstrom <[email protected]>

---------

Signed-off-by: Michael Carlstrom <[email protected]>
Co-authored-by: Tomoya Fujita <[email protected]>

Author: InvincibleRMC

source/Releases/Release-Lyrical-Luth.rst

@@ -39,6 +39,12 @@ TODO
 New features in this ROS 2 release
 ----------------------------------
 
+``rosidl_python``
+^^^^^^^^^^^^^^^^^
+
+Passing in Python ``set`` objects into array or sequence fields is now deprecated.
+Instead pass in something that implements ``collections.abc.Sequence`` most commonly a ``list``, ``tuple``, or a ``numpy.ndarray``. To be removed in ROS M.
+
 Development progress
 --------------------