[DOCS] Fix title and code example of changelog

The code example was not rendered, since a empty
line was missing.

Additionally, the title has to start with "Important:".

Resolves: #97072
Related: #93635
Releases: main, 11.5
Change-Id: I85b53f8d2f89558300b6ea996e1ab1147a678a92
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/73773


Tested-by: core-ci <typo3@b13.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>

typo3/sysext/core/Documentation/Changelog/11.5.x/Important-93635-AddMailConfigurationForSettingSmtpDomain.rst

 .. include:: ../../Includes.txt
 
-================================================================
-Bugfix: #93635 - Add mail configuration for setting smtp domain
-================================================================
+==================================================================
+Important: #93635 - Add mail configuration for setting smtp domain
+==================================================================
 
 See :issue:`93635`
 
@@ -43,6 +43,7 @@ Configuration Example for GSuite.
 Impact
 ======
 
-Now it is possible to set the smtp mail domain which is required for some relay-server.
+Now it is possible to set the smtp mail domain which is required for
+some relay-server.
 
 .. index:: LocalConfiguration, ext:core