[DOCS] Improve output of *rootPaths examples

Maybe there is also a better way to display this? Currently the line
breaks aren't visible, which makes it quite hard to understand.

https://docs.typo3.org/c/typo3/cms-form/main/en-us/D/FrontendRendering/Index.html

Releases: main, 12.4
Resolves: #102903
Change-Id: Ib363f2aa6145511b0ed244d140068bb32e68de15
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/82614


Tested-by: Nikita Hovratov <nikita.h@live.de>
Reviewed-by: Nikita Hovratov <nikita.h@live.de>
Tested-by: core-ci <typo3@b13.com>