Remove Version warning on stable

Describe the issue linked to the documentation

Current docs for stable have the version warning reserved for what are not the stable docs

We need to remove that

Suggest a potential alternative/fix

I think that the solution is to build the doc changing

Line 207 in 44c9a4d

"version_match": "dev",

        "version_match": "dev",

to stable

the version match isn't a string to say which is the stable version but rather a sphinx variable indicating what is the version of the docs currently being built. So it does need to be changed but I think to something like version rather than "stable"

https://pydata-sphinx-theme.readthedocs.io/en/stable/user_guide/version-dropdown.html#configure-switcher-version-match

however to be able to check we would need to fix the version.json first (I put 1.3 instead of 0.3): #1035

I think that it is the string used to match what's in the "version.json", so if we use "stable" in version.json, we can use "stable" in there too

Banner is gone:
https://skrub-data.org/stable/

Thanks!!