pythonPackages.notebook: fix darwin build
The send2trash library, which is now included in the notebook doesn't
succeed during build, even though it works.
(cherry picked from commit 8aaa17c52a1b07874a0cf4fb03d2ac3ca9e8c2ea)
authored by Josef Kemetmüller and committed by Daiderd Jordan 42e2ed65 a3983d6d