Fix Bug 1101220 - Developer Edition follow-ups

I'll check the all redirects later...
Sorry I have missed @pmclanahan's comment here somehow. That's what I previously [noted in the bug](https://bugzilla.mozilla.org/show_bug.cgi?id=1101220#c0). The channel name is still `aurora` but the release notes no longer mention that, so I thought we could change the `auroranotes` slug to the standard `releasenotes` one. Any thoughts?