[DOCS] Fix incorrect namespace of AbstractModule

The AbstractModule class is located within the 'ModuleApi' folder, so the
namespace must be \TYPO3\CMS\Adminpanel\ModuleApi\AbstractModule. This
patch fixes the issue.

Releases: main, 12.4
Resolves: #104204
Change-Id: I28dc1777fe8900665e8a3d43a8655674dbb82185
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/84846


Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: core-ci <typo3@b13.com>

typo3/sysext/adminpanel/Documentation/Extending/Index.rst

@@ -26,7 +26,7 @@ To create your own Admin Panel module
 =====================================
 
 #. Create a new PHP class extending
-   `\TYPO3\CMS\Adminpanel\Modules\AbstractModule`.
+   `\TYPO3\CMS\Adminpanel\ModuleApi\AbstractModule`.
 
 #. Implement at least the following methods: