Backport PR #56393 on branch 2.1.x (DOC: Add release date for 2.1.4) (#56395)

Backport PR #56393: DOC: Add release date for 2.1.4

Co-authored-by: Thomas Li <47963215+lithomas1@users.noreply.github.com>

Author: meeseeksmachine

doc/source/whatsnew/v2.1.4.rst

@@ -1,6 +1,6 @@
 .. _whatsnew_214:
 
-What's new in 2.1.4 (December ??, 2023)
+What's new in 2.1.4 (December 8, 2023)
 ---------------------------------------
 
 These are the changes in pandas 2.1.4. See :ref:`release` for a full changelog
@@ -14,7 +14,6 @@ including other versions of pandas.
 Fixed regressions
 ~~~~~~~~~~~~~~~~~
 - Fixed regression when trying to read a pickled pandas :class:`DataFrame` from pandas 1.3 (:issue:`55137`)
--
 
 .. ---------------------------------------------------------------------------
 .. _whatsnew_214.bug_fixes:
@@ -37,14 +36,6 @@ Bug fixes
 - Fixed bug in :meth:`Series.str.translate` losing object dtype when string option is set (:issue:`56152`)
 -
 
-.. ---------------------------------------------------------------------------
-.. _whatsnew_214.other:
-
-Other
-~~~~~
--
--
-
 .. ---------------------------------------------------------------------------
 .. _whatsnew_214.contributors: