[BUGFIX] Strip superfluous srcset path prefix

Rendering image '<source>' elements using the
IMAGE content object (layoutKey 'picture')
no longer have the document root path prepended
in the 'srcset' attribute.

Resolves: #100867
Related: #95379
Releases: main, 12.4
Change-Id: Id49b0f9a41dd9760e25fc17386cae805f66083e9
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/79030


Tested-by: core-ci <typo3@b13.com>
Tested-by: Ben Robinson <robinson2.ben@gmail.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>