[fr] Removing old CSS includes from K8s basics tutorials

[seifrajhi]

French tutorials still include old CSS files. However, if you visit these pages, the browser will try to access them and return 404 (e.g.).

They were removed from the English tutorials in #34188. This PR removes them from the French localisation.

PS: Not directly related to this PR, even though https://katacoda.com/embed.js was included on those pages next to the CSS files I did not remove them.

I also wanted to let you know that all Katacoda-related pieces should be removed from the localisation since these interactive tutorials are not supported anymore and need replacing. Here is an umbrella issue for this task #41496

To get rid of Katacoda, many texts need corrections, which I can't do without French team knowledge.

/sig docs
/language fr
/area localization

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