Update remote for authentication-free clone but ssh authenticated push.

What does this MR do?

Modify devdocs to use https for cloning and pulling, thus only requiring authentication on push.

How confident are you it won't break things if deployed?

100%

Links to related issues

Checklist

• added a test, or explain why one is not needed/possible...
• no unrelated changes
• asked someone for a code review
• joined #foodsharing-beta channel at https://slackin.yunity.org
• added an entry to CHANGELOG.md (description, merge request link, username(s))