DOC Update changelog before the 1.2.1 release

[jjerphan]

@ogrisel and I are preparing the 1.2.1 release.
We think those PRs have to be part of it and have changed the release note accordingly.

We also want to have #25114 #25131 #25129 and #25147 be part of this release, but those do not feature in the changelog (mostly because those are maintenance changes).

What do you think?

[thomasjpfan]

Here are my thoughts:

• ❌ FIX ignore *args and **kwargs in parameter validation of public functions #25114 : This introduces a new parameter constraint to train_test_split. I prefer not to introduce a new constraint in a bug fix release.
• ❌ FIX pos_label constraint in roc_curve (param validation) #25131 : Do not include because it adjusts the parameter constraints on roc_curve and those parameter constraints do not exist in 1.2.X
• ✅ FIX Remove spurious UserWarning #25129
• ✅ FIX Convert boolean pd.Series to boolean ndarrays #25147 (This is already in the changelog)

[jjerphan]

I agree with what @thomasjpfan suggests. Do you, @ogrisel?

[ogrisel]

Alright!

[jjerphan]

Based on @thomasjpfan's comment, the change-log does not need to be modified. I guess all the issues back-ported from 1.3 to 1.2.X are possible and that the PR is thus mergeable if the CI is green. WDYT?

[jjerphan]

FYI I have opened #25442 for releasing 1.2.1, and I am waiting for the current PR (i.e. #25436) to be merged before pursuing the release process.

[thomasjpfan]

LGTM

[jjerphan]

Thanks, @thomasjpfan!