Maybe 0.23 or 0.24? since current stable is 0.21.X.

Yes, of course, thanks. Changed back to 0.23.

0.24 and a what's new entry might be less controversial, but I'm OK with current version.

Well it was deprecated in 2015, 0.23 will be in 2020-2021. Other libraries typically deprecate something, then remove it after a while. scikit-learn started to indicate the exact deprecation version not that long ago I imagine, this code should have been removed long time ago.

Could you document it in what's new (under deprecation maybe), such that we easily spot if for removal in the next release?

Could you document it in what's new (under deprecation maybe)

I can add,

- |API| The "l1" and "l2" options of `loss` parameters in :class:`svm.LinearSVC`,
    :class:`svm.LinearSVR` that were deprecated in v0.16 will be removed in v0.23.
    :pr:`12916` by :user:`Roman Yurchak`_. 

but I don't think it makes much sense, because we don't typically make guarantees as to when a deprecated functionality will be removed (simply because we might very well forget to remove it in v0.23). Also the only thing changing in v0.22 is the content of the deprecation message. It's not an API change and mostly irrelevant to current users.

such that we easily spot if for removal in the next release?

Searching for 0.23 is probably a more reliable way of finding deprecations anyway?

Searching for 0.23 is probably a more reliable way of finding deprecations anyway?

Reliable yes but a headache as well :). If everything that should be removed for a version could be documented in a single section, it would ease the search :)