use version number instead of 'master' in html header title (#38149)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/38149
This is for (#21290) (#31894)
Instead of putting "Pytorch master documentation" in header's html title, now we use "Pytorch 1.x.x documentation", this is similar to tensorFlow and numpy doc page.
In google search, we will get
Pytorch Documentation - Pytorch 1.x.x Documentation instead.
Test Plan: Imported from OSS
Differential Revision: D21586559
Pulled By: glaringlee
fbshipit-source-id: 2995709ac3c22dbb0183b5b4abfde7d795f1f8eb
