docs: remove empty section titles

Author: kenjis

user_guide_src/source/changelogs/v4.3.2.rst

@@ -23,18 +23,12 @@ without a trailing slash (``/``) like ``http://localhost:8080``. Now it returns
 baseURL with a trailing slash. This is the same behavior as ``base_url()`` in
 CodeIgniter 3.
 
-Message Changes
-***************
-
 Changes
 *******
 
 - The parameter ``$relative`` in :php:func:`uri_string()` was removed. Due to a bug,
   the function always returned a path relative to baseURL. No behavior changes.
 
-Deprecations
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-
 Bugs Fixed
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