[OMPT] Fix typo in test parallel/nested_thread_num.c
[OMPT] Fix typo in test parallel/nested_thread_num.c

This caused test failures with GCC since its initial commit in
r336085 (https://reviews.llvm.org/D46533).

git-svn-id: f99161ee8ccfe2101cbe1bdda2220bce2ed25485@337911 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/openmp,llvm-mirror/openmp,llvm-mirror/openmp,llvm-mirror/openmp,llvm-mirror/openmp