[OpenMP] [Tests] Update test broken by #157364 (#158751)

Fix another test impacted by #157364.

On Windows, `GetComputerNameA()`, which is what this ends up calling,
takes an `LPDWORD`, but we were handing it an `int*`; fix this by
declaring it as a `DWORD` instead.

GitOrigin-RevId: eb1297910e361628719c1c5d81e60ca4e32fb64f