[TASK] Remove deprecated code

Remove the deprecated StandardDocumentTemplate

Change-Id: I2f2d08da9134b65b27058d0b072d642c6ac34a34
Resolves: #46954
Releases: 6.1
Reviewed-on: https://review.typo3.org/20087
Reviewed-by: Markus Klein
Reviewed-by: Stefan Neufeind
Reviewed-by: Benjamin Mack
Tested-by: Benjamin Mack