Fixing xlm example docts (#776)
Fixing xlm example docts (#776)

Summary:
Resolves #762
Pull Request resolved: https://github.com/pytorch/fairseq/pull/776

Differential Revision: D15631503

Pulled By: lematt1991

fbshipit-source-id: 103f77d553476917b8b0f8001767217fb311d920

pytorch/fairseq,pytorch/fairseq,pytorch/fairseq