[BUGFIX] Remove invalid definition of method body functionality

The method parseDataStructureByIdentifier defines that files can
also be loaded with the "EXT:" prefix. This is currently not
supported and not documented, thus should be removed. The only
valid syntax is with "FILE:EXT:"

Resolves: #92483
Releases: main, 11.5
Change-Id: I5156c40215753566251c56ca0cbd9b94b66ce4a0
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/74441


Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Benni Mack <benni@typo3.org>