The Core still calls tslib_fe->ADMCMD_preview() in index_ts.php.
Remove the whole code block, since this has been moved to Tx_Version.

The corresponding function in Tx_Version_Preview is already called in
the connectToDB hook.

Change-Id: I24152ecd3183a17257eb79a58f5270d0fce3a04d
Fixes: #31290
Relates: #27931
Releases: 4.7, 4.6
Reviewed-on: http://review.typo3.org/6344
Reviewed-by: Oliver Klee
Reviewed-by: Simon Schaufelberger
Tested-by: Simon Schaufelberger
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer
Reviewed-by: Andreas Wolf
Tested-by: Andreas Wolf