Remove duplicated release note.

Author: anthony-tuininga

doc/src/release_notes.rst

@@ -42,8 +42,6 @@ Thin Mode Changes
 #)  The thread that closes connection pools on interpreter shutdown is now only
     started when the first pool is created and not at module import
     (`issue 426 <https://github.com/oracle/python-oracledb/issues/426>`__).
-#)  Added support for Transaction Guard by adding support to get the values of
-    :attr:`Connection.ltxid` and :attr:`oracledb._Error.isrecoverable`.
 #)  Support for :ref:`Pipelining <pipelining>` is no longer considered a
     pre-release.
 #)  Fixed hang when attempting to use pipelining against a database that