Fix when giving jit format warning about unsupported options (#28616)
Summary:
Current reges also matches strings with '{}' so warning is always given.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/28616
Test Plan: Previous code was giving a warning about unspported options, these disappeared. When adding something inside '{}' the warning came back.
Differential Revision: D18039443
Pulled By: ggoossen
fbshipit-source-id: bb3a2892d5707a32030d43250c40f3058aa1d18b
