Fix ICE in `cuda_sender_test` with ROCm Clang-15

[aurianer]

Compiler error: https://cdash.cscs.ch/test/66321134. Triggered by triggered by the call to vm.count("seed") (https://github.com/pika-org/pika/blob/87b10a0b70973cbaf164c46118444839501e0d56/libs/pika/async_cuda/tests/unit/cuda_sender.cu#L129).