Update ruby Docker tag to v3.4

[renovate]

This PR contains the following updates:

Package	Update	Change
ruby	minor	3.3 -> 3.4

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[straight-shoota]

This is a reiteration of #882 which was originally reverted in #885. But now after updating to Jekyll 4.4 (#893) we should be fine to upgrade Ruby.

[ysbaddaden]

Allright, I'll trust you 🤞