Remove unused variable, prefer toLatin1().data()
Remove unused variable, prefer toLatin1().data()

The scalar opacity function isn't used anymore, and we prefer
toLatin1().data() for QString conversion to const char*.

Signed-off-by: Marcus D. Hanwell <cf7042e2e8eee958b5bcde1ae2cbefef82efc184@kitware.com>

OpenChemistry/tomviz,OpenChemistry/tomviz,OpenChemistry/tomviz,OpenChemistry/tomviz