[BUGFIX] Fix extension path in ComposerDeficitDetector

Instead of relying on a hard coded extension install path,
now the real extension path is used provided by the package manager

Releases: main, 11.5
Resolves: #96375
Change-Id: Ic2e4d71413416a5271420e939e5f74fa28cbaca6
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/72697


Reviewed-by: Simon Gilli <typo3@gilbertsoft.org>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Mathias Brodala <mbrodala@pagemachine.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Helmut Hummel <typo3@helhum.io>
Tested-by: Simon Gilli <typo3@gilbertsoft.org>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Helmut Hummel <typo3@helhum.io>