Update diagnose tests submodule (#758)
Update diagnose tests submodule (#758)

Update it to the latest version that includes fixes for Node.js and
Elixir. Update it here so we're sure it is accurate for all
integrations.

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[skip changeset]
appsignal/appsignal-ruby,appsignal/appsignal-ruby,appsignal/appsignal-ruby,appsignal/appsignal-ruby