Remove note about `symbol.tree.info` in `Quotes`

[cchantep]

https://github.com/lampepfl/dotty/blob/bed1c4aadc0efd32ceeeb3b76f487da664c6287d/library/src/scala/quoted/Quotes.scala#L3480

[nicolasstucki]

@liufengyun, you added that comment. Could you update it?