[BUGFIX] Mention correct class and function in rst file

Due to a copy-paste error, the description of the documentation
file does not reflect the other parts.

Resolves: #76259
Releases: master, 8.7
Change-Id: Iea069cae225523d3d35eb6b41b4ab618f2c25e76
Reviewed-on: https://review.typo3.org/54947


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>