fix typo (#1553)
fix typo (#1553)

Summary: Pull Request resolved: https://github.com/facebookresearch/faiss/pull/1553

Reviewed By: mdouze

Differential Revision: D25704031

Pulled By: beauby

fbshipit-source-id: d5a632a529ad71b40a583340a383071e74c356da

facebookresearch/faiss,facebookresearch/faiss,facebookresearch/faiss,facebookresearch/faiss