[exportdb] Fix generating docs (#107838)
Previously I accidentally replaced all `=` with `-`, resulting in clowny code rendering like:
The purpose of replacing the `=` with `-` is to change the RST heading size of modules. So now, I replace strings with more than 3 `=`'s with `-`. This should avoid incorrectly replacing code where we set variables with `=` and do equality checks with `==`.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/107838
Approved by: https://github.com/gmagogsfm
