DuckDns docs: add https hint and fix typo

[leschekfm]

Description:

After installing duckdns, adding the certificates, adjusting the config and restarting hassbian I was wondering why reloading my already opened tab with hassbian.local:8123/ was returning nothing.
Then I searched for any errors in the console logs or if I screwed up anywhere else.
I probably would have noticed earlier that I first needed to change the protocol in the URL if Chrome wasn't hiding the protocol nowadays...

Therefore I think a hint can spare others some time searching for errors.

While at it I also fixed a minor typo.

Checklist (Required):

• The code change is tested and works locally.
• The code is compliant with Contributing guidelines

If pertinent:

• Script has validation check of the job.
• Created/Updated documentation at /docsth

[ludeeus]

You only need to restart Home Assistant, not hassbian I changed that in your branch.
Other than that it looks good :)
Thanks! 🥇