[TASK] Remove renamed language command controller

Follow-up to 0d69c2d9e7b89ea63522d0b5e54aadf20ec1245d.

The renamed language command controller (language:update) was introduced
in 6.2, so we can simply remove the original name instead of deprecating
it.

This will only affect installations which are already using this task
since 6.2 alpha2.

Resolves: #54128
Releases: 6.2
Change-Id: Id6bb709bd30c9044c949c431aa2a595c1035c601
Reviewed-on: https://review.typo3.org/28433
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer