Disable searching the Asset Store in Project Window's search box?

How do I disable “Searching the Asset Store” when entering text into the search box of “The Project Window”?

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It really annoys me because it freezes the whole editor for some time and the results are completely useless for what I’m doing when searching things in my own project.

As of Unity 2018.1.1f1 you can disable Asset Store search in Preferences:

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