Resolve runtime warning

[baltzell]

In file included from input_line_14:1:
In file included from /u/group/clas12/packages/clas12-mcgen/3.01/clas12-elSpectro/src/C12Utils.h:4:
/group/clas12/packages/clas12-mcgen/3.01/clas12-elSpectro/elSpectro/core/LundWriter.h:27:20: warning: class with destructor marked 'final' cannot be inherited from [-Wfinal-dtor-non-final-class]
     ~LundWriter() final;
                   ^
/group/clas12/packages/clas12-mcgen/3.01/clas12-elSpectro/elSpectro/core/LundWriter.h:16:9: note: mark 'elSpectro::LundWriter' as 'final' to silence this warning
  class LundWriter : public Writer {
        ^

[dglazier]

This looks like an elspectro warning not clas12root.
It is a non-urgent fix, newer compilers prefer if the class is labelled final if the destructor is.It should be fixed next time I update clas12-elspectro