Specify the needed devdocs artifacts correctly

What does this MR do?

Currently, the devdocs "artifacts" are defined as the woule docs folder. Correct is, that the Artifacts are:

• .docusaurus
• book
• build
• dist
• node_modules

Because we don't run any tests etc. and it is a static site only build is needed (see .gitlab-ci.yml#L371

How confident are you it won't break things if deployed?

Quite sure but not tested

How to test

Don't know

Checklist

• added a test, or explain why one is not needed/possible...
• no unrelated changes
• asked someone for a code review
• set a "for:" label to indicate who will be affected by this change
• added to the next milestone (see https://gitlab.com/foodsharing-dev/foodsharing/-/milestones, unless it has a "for:Dev" label)
• added an entry to CHANGELOG.md
• [Not Needed] added a short text that can be used in the release notes