Change search-actors description, when users search for top or best Actors the query should be empty

[jirispilka]

The search should be performed without keywords, otherwise it will return results not matching user intent

Let's not over-engineer it.

• Try to tighten the search-actors tool description with a hint how Actors are sorted by default
• Play with it
• If ok, release it, if we are not able to fix it, let's close it