Creating the branch to start the necessary cleanups before the release, while the remaining issues in https://github.com/scikit-learn/scikit-learn/milestones/0.23 are managed.

• update news and what's new date in master and release branch
• create tag
• update dependencies and release tag at https://github.com/MacPython/scikit-learn-wheels
• twine the wheels to PyPI when that's green
• https://github.com/scikit-learn/scikit-learn/releases draft
• confirm bot detected at https://github.com/conda-forge/scikit-learn-feedstock and wait for merge
• https://github.com/scikit-learn/scikit-learn/releases publish
• fix the binder release version in .binder/requirement.txt (see [MRG] More explicit binder requirements for 0.22 #15847)
• announce on mailing list and on twitter