refactor: Simplify expander print view styling

[therobrob]

1. removed arrow-icon from print view (was shown in booking-expanders)
2. refactored open-status with pseudo-selector ::details-content
3. some general code refactoring

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[github-actions]

Hi there! 👋

Thank you for your contribution to the FIP Guide! 🚀
We appreciate your effort in making rail staff travel information more accessible. 🚄

Checklist before merging:

• Added a description to the Pull Request
• Checked the License of new pictures (non-commercial use without attribution)
• Modified content in English
• Modified content in German
• Modified content in French

[MoritzWeber0]

Really cool! 🥳

[therobrob]

now the icons are centered on multi-line-headings either 🙈 But we can also leave it as it is.

[MoritzWeber0]

now the icons are centered on multi-line-headings either 🙈 But we can also leave it as it is.

But it's consistent with how we do it for the train categories too. Let's leave it for this PR and if there is a need, we can open it as additional PR or track it as issue.