[cxx-interop] Adjust a concepts test for rebranch
Clang now includes concepts in the mangled names of C++ functions: https://github.com/apple/llvm-project/commit/4b163e343cfa54c8d55c9da73c70d58f55ea9df2
This adjusts the test to verify that we don't transitively emit the symbols referenced from the requires expression. Those symbols shouldn't be emitted because they are not executed.
rdar://127263407
