[TASK] Update autoprefixer, postcss and raise minimum IE version

This patch updates autoprefixer, postcss and raises the minimum IE
version to 11.

Resolves: #72482
Releases: master
Change-Id: I5a3c2a37a55ec853701ef0eb4f7b7a06a16cbd43
Reviewed-on: https://review.typo3.org/45509


Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>