[FOLLOWUP][TASK] Deprecate some functions not in use anymore in the core

Update the RST file

Resolves: #72851
Releases: master
Change-Id: I86e6490ed8299c9e5fb817decb430a2017105214
Reviewed-on: https://review.typo3.org/46146


Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Tested-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Frank Nägler <frank.naegler@typo3.org>
Tested-by: Frank Nägler <frank.naegler@typo3.org>