Fix small memory leak regarding __kmp_nested_proc_bind

There is no corresponding free() for this expandable array.  The logic is
added in __kmp_cleanup() next to the freeing of __kmp_nested_nth.


git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@292348 91177308-0d34-0410-b5e6-96231b3b80d8