cupy needs a fix for `isin` with scalar arguments

[ev-br]

array_api_tests/test_set_functions.py::TestIsin::test_isin_scalars is failing with array_api_compat.cupy. Needs to either follow cp.searchsorted and add a shim, or xfail the test.

[ev-br]

#396 added a shim, now need to follow up with the upstream cupy

[prady0t]

Has this been fixed yet?