Remove `VerboseLevel:' parameter from TMVA weights files

`VerboseLevel:' parameter is not supported by newer version of ROOT5
and ROOT6. It blocks ROOT6 RelVals from running.

Initially reported in OfflineComputingPlanningMeeting2013121.

Signed-off-by: David Abdurachmanov <David.Abdurachmanov@cern.ch>
Merge pull request #2377 from davidlt/remove-VerboseLevel-from-TVMA-weights-file

Remove `VerboseLevel:' parameter from TMVA weights files