Fix zen mode karma test

Zen mode spec fails to run separately

Reasons:

• we are not initializing notes in spec. Component was consuming some weird HTML before
• our fixture generator cuts script with application/json lang, which is required for notes initialization

See #67206 (moved) for details

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry for user-facing changes, or community contribution. Check the link for other scenarios.
• [-] Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content