Changelog for 0.71.0 (facebook#35200)

Summary:
Adds changelog for new release.

## Changelog

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[Internal] [Changed] - add changelog entry for 0.71.0

Pull Request resolved: facebook#35200

Test Plan: N/A

Reviewed By: dmytrorykun

Differential Revision: D42477941

Pulled By: cipolleschi

fbshipit-source-id: be91742d8800051b9b167b66592b43e715b9a893