xds/csds: unskip test after ADS stream flow control changes are merged

[easwars]

In https://github.com/grpc/grpc-go/pull/7347, we added a t.Skip for arm64 in TestCSDS. See: https://github.com/grpc/grpc-go/blob/4e9b5968af1aeffb0cb44e772aa69a4b4e44a722/xds/csds/csds_e2e_test.go#L156

Once https://github.com/grpc/grpc-go/issues/7382 is fixed, we should be able to fix this test to not require a skip.