[DOCS] Remove index page from changelogs

The index file in its current state does not has any value to the user.
Mostly numbers are displayed as reference.

Resolves: #102996
Releases: main, 12.4
Change-Id: I6a4c52e5c295bb27f5fd85045f2c3f9451bea1e5
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/82733


Reviewed-by: Benjamin Franzke <ben@bnf.dev>
Tested-by: Benjamin Franzke <ben@bnf.dev>
Tested-by: core-ci <typo3@b13.com>

typo3/sysext/core/Documentation/Index.rst

@@ -57,4 +57,3 @@ documented here.
    :hidden:
 
    Sitemap
-   genindex

typo3/sysext/core/Documentation/genindex.rst

-.. include:: /Includes.rst.txt
-
-=====
-Index
-=====
-
-.. Sphinx will insert here the general index automatically.