UHF-11225: Removed everything related to chat leijuke

[annadruid]

UHF-11225

What was done

• Removed everything related to chat leijuke since hammashoito was the only one using it anymore

How to install

• Make sure your instance is up and running on latest dev branch.
  • git pull origin dev
  • make fresh
• Update the HDBT theme
  • composer require drupal/hdbt:dev-UHF-11225
• Run make drush-cr

How to test

• See platform config pr
• Check that code follows our standards

Continuous documentation

• This feature has been documented/the documentation has been updated
• This change doesn't require updates to the documentation

Translations

• Translations have been added to .po -files and included in this PR

Other PRs

• UHF-11225: Removed everything related to chat leijuke drupal-helfi-platform-config#882

[khalima]

All other chats seem to work normally. Let's merge this once the "Sotebotti Hester" is in use. 🚀

[khalima]

Setting this PR as "Request changes" to prevent accidental merge. The PR has been tested and approved, but it shouldn't be merged until the Sotebotti Hester is in use. See the ticket.