chore: replace special whitespace chars
Description
This MR adds the Kubernetes introduction video link and embed to the onboarding course
Context
https://tasks.opencraft.com/browse/SE-5760
Test instructions
- Check that the video is available at the bottom of the page: https://preview.courses.opencraft.com/courses/course-v1:OpenCraft+onboarding-dev+course/courseware/task_specific/9143c123bb264ef490687dfc1c550e0d/1?activate_block_id=block-v1%3AOpenCraft%2Bonboarding-dev%2Bcourse%2Btype%40vertical%2Bblock%4002e15013ad6a45848f2bb16e0362bace
Edited by Boros Gábor