Fix sklearn tests

[schlunma]

Description

Due to a recent update of scikit-learn, some of our tests fail.

This PR fixes that by

• adapting the our code to the changes of their public API
• not using private API anymore to avoid errors like this in the future

• Closes #3504

• • *

Before you get started

• [x] ☝ Create an issue to discuss what you are going to do

Checklist

It is the responsibility of the author to make sure the pull request is ready to review. The icons indicate whether the item will be subject to the 🛠 Technical or 🧪 Scientific review.

• [x] 🛠 This pull request has a descriptive title
• [x] 🛠 Code is written according to the code quality guidelines
• [x] 🛠 Documentation is available
• [ ] 🛠 ~Tests run successfully~ see https://github.com/ESMValGroup/ESMValTool/pull/3506#issuecomment-1905992518
• [x] 🛠 The list of authors is up to date
• [x] 🛠 Any changed dependencies have been added or removed correctly
• [ ] 🛠 ~All checks below this pull request were successful~ see https://github.com/ESMValGroup/ESMValTool/pull/3506#issuecomment-1905992518

New or updated recipe/diagnostic

• [x] 🧪 Recipe runs successfully
• [x] 🧪 Recipe is well documented
• [x] 🧪 Figure(s) and data look as expected from literature
• [x] 🛠 Provenance information has been added

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[schlunma]

I guess the CircleCI tests are failing due to the outdated docker container, the tests run fine locally and on GitHub actions 👍

I will test one recipe, then we can merge this.

[valeriupredoi]

indeed that's why, Manu - cheers, ping when you ready so I merges

[schlunma]

Recipes ran successful and output looks good, this can be merged 👍

[valeriupredoi]

legend Manu :beer: