Currently google serves the dev-docs as the standard results.
To avoid that, you can use rel="canonical" links.
There's a simple change to the sphinx template you can use:
https://github.com/scikit-learn/scikit-learn/blob/master/doc/themes/scikit-learn/layout.html#L29

<link rel="canonical" href="http://scikit-learn.org/stable/{{pagename}}.html" />