Change namespace in sample Atom feed to HTTP

[jake-penguins]

Overview

Changes the line <feed xmlns="https://www.w3.org/2005/Atom" xml:lang="{channel_language}"> to <feed xmlns="http://www.w3.org/2005/Atom" xml:lang="{channel_language}"> in the sample Atom feed template.

Feed parsers expect the namespace to use HTTP and will not read the feed if the namespace uses HTTPS. E.g. when attempting to test one of my websites' feeds in Miniflux, it gave the error:

Unable to parse Atom feed: "expected element <feed> in name space http://www.w3.org/2005/Atom but have https://www.w3.org/2005/Atom"

https://tt-rss.org/myfeedsucks/ also could not read the feed.

Nature of This Change

• [x] 🐛 Fixes a bug
• [ ] 🚀 Implements a new feature
• [ ] 🛁 Rewrites existing documentation
• [ ] 💅 Fixes coding style
• [ ] 🔥 Removes unused files / code