Remove const_cast in BTagSecVertexing.

http://goetz.web.cern.ch/goetz/mutable_2019-07-13.html#[jJ]et_BTagging

nightly/master/2019-07-13T2149:PhysicsAnalysis/JetTagging/JetTagAlgs/BTagging/src/BTagSecVertexing.cxx +695

   693	    xAOD::BTaggingContainer::iterator btagIter=btaggingContainer->begin();
   694	    for (xAOD::JetContainer::const_iterator jetIter = jetContainer->begin(); jetIter != jetContainer->end(); ++jetIter, ++btagIter) {
   695	      //temporary const_cast
   696	      xAOD::Jet& jetToTag = const_cast<xAOD::Jet&>( **jetIter );
   697	      ToolHandleArray< InDet::ISecVertexInJetFinder >::const_iterator itSecVtxFinders = m_secVertexFinderToolsHandleArray.begin();
nightly/master/2019-07-13T2149:PhysicsAnalysis/JetTagging/JetTagAlgs/BTagging/src/BTagSecVertexing.cxx +696

   694	    for (xAOD::JetContainer::const_iterator jetIter = jetContainer->begin(); jetIter != jetContainer->end(); ++jetIter, ++btagIter) {
   695	      //temporary const_cast
   696	      xAOD::Jet& jetToTag = const_cast<xAOD::Jet&>( **jetIter );
   697	      ToolHandleArray< InDet::ISecVertexInJetFinder >::const_iterator itSecVtxFinders = m_secVertexFinderToolsHandleArray.begin();
   698	      ToolHandleArray< InDet::ISecVertexInJetFinder >::const_iterator itSecVtxFindersEnd = m_secVertexFinderToolsHandleArray.end();

RunTier0Tests.py was fine. RunTier0Tests.log