[TASK] Remove last mentions of Less in the core

Resolves: #80529
Releases: master
Change-Id: Ic90bf297baad33576509f9ff13ab67674ba658ac
Reviewed-on: https://review.typo3.org/52221


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Jigal van Hemert <jigal.van.hemert@typo3.org>
Tested-by: Jigal van Hemert <jigal.van.hemert@typo3.org>
Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Tested-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Benjamin Kott <benjamin.kott@outlook.com>
Tested-by: Benjamin Kott <benjamin.kott@outlook.com>