The library was removed with 6.0, source mention is not needed anymore.

Change-Id: Icae1c37409e914cd55b9f20eff0f548ec3515e07
Resolves: #41265
Releases: 6.0
Reviewed-on: http://review.typo3.org/14942
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn