[OpenMP] Enable the 'libc/malloc.c' test on NVPTX

Summary:
Previously this test hanged indefinitely on NVPTX. This was due to an
issue fixed previously where we would wait indefinitely inside the CUDA
runtime waiting for the kernel to complete if it was blocked on the RPC
server. This patch enables this test again now that it can run without
deadlocking, at least on CUDA 12.2.