Remove notebook from required library dependencies #1713
Description
In PR #1217 the jupyter metapackage was added as a core library dependency (for what seems like a convenience factor?) and in PR #1337 this was switched to notebook <=6.4.12. As of https://github.com/sbi-dev/sbi/tree/33168887e892e9e08b19ae421e15e15c902b6509 there is no sbi library code that depends on the library mechancis of the notebook library. As sbi the library does not require the notebook library at runtime, notebook should not be a core library dependency but instead should be moved to an extra or to a dependency group if needed only for tests.