[!!!][TASK] Remove GeneralUtility::stdAuthCode

GeneralUtility::stdAuthCode is unused since at
least v9 and is therefore now removed.

Resolves: #96140
Related: #94309
Releases: main
Change-Id: Idc68fff1c946e7f2f30645a6a3510d95f8e272bf
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/72375


Tested-by: core-ci <typo3@b13.com>
Tested-by: Nikita Hovratov <nikita.h@live.de>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Nikita Hovratov <nikita.h@live.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Benni Mack <benni@typo3.org>