Switch to different PHP package for the calendar

Part of #1065 (closed)

What does this MR do?

Switches from welpdev/icalBundle to the underlying jasvrcek/ICS package, which is PHP8 compatible (https://github.com/jasvrcek/ICS/issues/59).

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

Quite sure, seems to work

How to test

1. Checkout branch locally
2. Login as foodsaver
3. Sign into some pickup slots
4. Go to the calendar page in the settings
5. Create a token and open the calendar link

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
• used "state:" labels to track this MR's state until it was beta tested
• 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
• added a short text that can be used in the release notes
• Once your MR has been merged, you are responsible to create a testing issue in the Beta Testing forum: https://foodsharing.de/?page=bezirk&bid=734&sub=forum. Please change the MRs label to "state:Beta testing".
  • Consider writing a detailed description in German.
  • Describe in a few sentences, what should be tested from a user perspective.
  • Also mention different settings (e.g. different browsers, roles, ...) how this change can be tested.
  • Be aware, that also non technical people should understand.

Release notes text in German