Fix namespace typo. (#16021)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16021
Adds nom:: so that TRIVIAL_CONVERTER works more generally.
Reviewed By: janewangfb
Differential Revision: D13664748
fbshipit-source-id: 100f47a8326e41bd0ac2ae281669f5a0363fe060
