Update holiday_calendars.json to be in sync with Thunderbird

[nclm]

From conversation in #6011:

Imported content from https://github.com/thunderbird/thunderbird-website/blob/master/media/caldata/autogen/calendars.json (version from Apr 1, 2024, 9:39 PM GMT+2) bringing the number of calendars from about 56 to about 86.

Adds 'locale', 'language', and 'updated' fields that are not used by Nextcloud at the moment but present in Thunderbird’s source file.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 23.54%. Comparing base (e44de16) to head (c472a85).
Report is 39 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #6014   +/-   ##
=========================================
  Coverage     23.54%   23.54%           
  Complexity      455      455           
=========================================
  Files           246      246           
  Lines         11707    11707           
  Branches       2141     2141           
=========================================
  Hits           2756     2756           
  Misses         8637     8637           
  Partials        314      314           

Flag	Coverage Δ
javascript	15.18% <ø> (ø)
php	58.46% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[miaulalala]

The problem is see is that old subscriptions aren't updated to the new endpoint, which means even if I have a subscription, the button in the subscription calendar list isn't greyed out. Instead I can subscribe to the same holiday calendar twice - in my test case for Germany. That's a bit confusing for the users.

Looks like the subscription is found in \Sabre\CalDAV\Backend\SubscriptionSupport::getSubscriptionsForUser.

I think this will need a bit of a code change in the backend, maybe a migration step that updates the subscriptions to use the new autogen endpoint automatically.

[github-actions]

Hello there,
Thank you so much for taking the time and effort to create a pull request to our Nextcloud project.

We hope that the review process is going smooth and is helpful for you. We want to ensure your pull request is reviewed to your satisfaction. If you have a moment, our community management team would very much appreciate your feedback on your experience with this PR review process.

Your feedback is valuable to us as we continuously strive to improve our community developer experience. Please take a moment to complete our short survey by clicking on the following link: https://cloud.nextcloud.com/apps/forms/s/i9Ago4EQRZ7TWxjfmeEpPkf6

Thank you for contributing to Nextcloud and we hope to hear from you soon!