[!!!][TASK] Remove renderCharset option

The renderCharset TypoScript option is used for internal
parsing of data coming from various sources (TypoScript,
Language Labels, Database, POST variables). As TYPO3
can only operate with UTF-8 in language files for the backend, and expects a UTF-8 compliant database,
the option is now always set to "utf-8" and cannot be changed.

Resolves: #73794
Releases: master
Change-Id: I4405e701567e65d31d290d0c9d922c38c7fc8cf3
Reviewed-on: https://review.typo3.org/46979


Reviewed-by: Daniel Maier <dani-maier@gmx.de>
Tested-by: Daniel Maier <dani-maier@gmx.de>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>