fix(recording): Fix transcription opt-in

[nickvergessen]

☑️ Resolves

Before:

var_dump(!'no' === 'yes');
bool(false)

var_dump(!'yes' === 'yes');
bool(false)

🏁 Checklist

• ⛑️ Tests (unit and/or integration) are included or not required
• 📘 API documentation in docs/ has been updated or is not required
• 📗 User documentation in https://github.com/nextcloud/documentation/tree/master/user_manual/talk has been updated or is not required
• 🔖 Capability is added or not needed

[nickvergessen]

/backport to stable27