💻 Delete tutorials

[boryanagoncharenko]

This PR removes tutorials including the content and the reference from the teacher's manual.

Fixes #5991

How to test

• All pages should load without an error especially the /hedy and /tryit pages
• The teacher's manual should not have a reference to the tutorial
• The localhost:8080/tutorial#default should not trigger the tutorial but return a 404

[jpelay]

Everything seems cool, but I don't think the changes to the slides library were intentional

[mergify]

Thank you for contributing! Your pull request is now going on the merge train (choo choo! Do not click update from main anymore, and be sure to allow changes to be pushed to your fork).

[mergify]

Thank you for contributing! Your pull request is now going on the merge train (choo choo! Do not click update from main anymore, and be sure to allow changes to be pushed to your fork).