Many of the marionette tests fail in non-english Tor Browser 8.0 builds
Running marionette tests on Tor Browser 8.0 builds others than english fails because the language prompt is shown.
We are setting extensions.torbutton.prompted_language to true to avoid this prompt. However a new language prompt has been integrated in ESR60, and the prompt shown by torbutton has been removed in legacy/trac#26409 (moved).