[SHMEM 1.6 Sec. 9.11] Sychronization

[stewartl318]

Summary of changes

Fix duplicate text in the description for shmem_test_all_vector

In the API description for shmem_test_all_vector there is duplicate text that says when nelems is 0 the function returns 1.

Proposal Checklist

• [ ] Link to issue(s)
• [ ] Changelog entry
• [ ] Reviewed for changes to front matter
• [ ] Reviewed for changes to back matter