[RemoveDIs] Update ConvertDebugDeclareToDebugValue after #72276 (#73508)

That patch was missing a recent change to the non-DPValue StoreInst overload.
Add it to the DPValue version. This is tested by
`llvm/tests/Transforms/Mem2Reg/dbg_declare_to_value_conversions.ll`,
which already has `--try-experimental-debuginfo-iterators`. It doesn't
fail currently because until #74090 lands the declares are not converted
to DPValues.

The tests will become "live" once #74090 lands (see for more info).