[TASK] Remove autoload-dev classmap configuration

After all test extensions received proper composer.json files,
they can be autoloaded via PSR-4. The classmap is therefor unused
and can be removed.

Resolves: #100825
Releases: main, 12.4
Change-Id: I83251a53bedd4f640af323ed88afdd2aa8db85a3
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/78957


Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Stefan Bürk <stefan@buerk.tech>