[clang][OpenMP] Fix crash on `lastprivate` of a data member in a member function template (#237575)
Fixes #144302
`lastprivate(i)` on a data member inside a member function template of a
non-template class crashed in `EndOpenMPDSABlock`. In a dependent
context the clause keeps the member as the `this->i` expression, but the
finalizer cast every non-dependent item to `DeclRefExpr`.
Skip the member there and leave its private copy to be built when the
template is instantiated, where the member gets captured as usual.
LLM Aided.