Increase line-width of Declarations.yaml (#18050)

Increase line-width of Declarations.yaml (#18050)

Summary:
There are some line breaks in schema_string of Declarations.yaml.
Is this valid yaml? I am reading yaml-spec.
It seems that the “|” indicator or single/double quote is required to insert line-break.
https://yaml.org/spec/1.2/spec.html
![image](https://user-images.githubusercontent.com/2469618/54405834-1e53ac80-471b-11e9-9925-be13a109eb46.png)
Could you increase line-width of yaml to avoid newline?
Pull Request resolved: https://github.com/pytorch/pytorch/pull/18050

Differential Revision: D14516694

Pulled By: ezyang

fbshipit-source-id: 1db9f3bf131b54a783d668de973915892603189e