docs: set_allow_multiselect is now correctly documented

[Jaskowicz1]

This PR corrects the documentation for set_allow_multiselect as it had the same documentation as set_duration.

Code change checklist

• I have ensured that all methods and functions are fully documented using doxygen style comments.
• My code follows the coding style guide.
• I tested that my change works before raising the PR.
• I have ensured that I did not break any existing API calls.
• I have not built my pull request using AI, a static analysis tool or similar without any human oversight.

[netlify]

✅ Deploy Preview for dpp-dev ready!

Name	Link
🔨 Latest commit	a54a7b9
🔍 Latest deploy log	https://app.netlify.com/sites/dpp-dev/deploys/6665aa30cbb6850008957c47
😎 Deploy Preview	https://deploy-preview-1162--dpp-dev.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.