[openmp][tests] Fix bug63197.c (#183508)
#183269 tried to fix the test, but the test can still randomly fail. The
OpenMP spec does not prevent the runtime to chose a smaller team size
than returned from omp_max_threads() for the second parallel region.
Using a larger value than `omp_max_threads()` in a `num_threads` clause
is valid OpenMP code. With a correct OpenMP implementation, the
team-size of the second parallel region must still be smaller or equal
the value returned from `omp_max_threads()`.
