[🍒][libcxx][nfc] Fix the ASAN bots: update expected.pass.cpp.

Ensures that `get_return_object`'s return type is the same as the return type for the function calling `co_return`. Otherwise, we try to construct an object, then free it, then return it.

Differential Revision: https://reviews.llvm.org/D103196

(cherry picked from commit 52123c96)