Revert "[BUGFIX] Check for incompatible SQL modes"

The sysenv-check is not the proper place for a check that needs a working db-connection. But we'll find a different place for this check shortly and then reintroduce it.

This reverts commit e727d5ff0b8ee93de38983555164b19f6bf87377

Change-Id: I117f38df6796bf04c285d6d5345a0829f32fbfc3
Reviewed-on: https://review.typo3.org/23242
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind