[flang][hlfir] Removed incorrect clean-up in the implied-do lowering.

[flang][hlfir] Removed incorrect clean-up in the implied-do lowering.

The lowering of calls/expressions unconditionally inserts DestroyOp
clean-up for hlfir.expr values, which is wrong in the case where
the value is used as a result of the elemental operation created
during the implied-do lowering. A cleaner fix could be to avoid
DestroyOp insertion at all, but I have not figure out an easy
way to do it. The DestroyOp look-up I used seems to be quite
reliable, so it should just work.

Reviewed By: clementval

Differential Revision: https://reviews.llvm.org/D155665