rev_news: improve outline

- Rename the "Outside the list" to "Other news" - Rename "Discussions" to "From the mailing list"

Author: tfnico

rev_news/draft/edition-2.md

@@ -17,22 +17,18 @@ You can contribute to the upcoming edition by sending [pull
 requests](https://github.com/git/git.github.io/pulls) or opening
 [issues](https://github.com/git/git.github.io/issues).
 
-## Discussions
+## From the mailing list
 
 ### General
 
-
 ### Reviews
 
-
 ### Support
 
-
 ## Misc Git News
 
 ### Developers
 
-
 ### Events
 
 *[Git Merge 2015](http://git-merge.com/), The Conference for the Git
@@ -44,7 +40,7 @@ Jeff King &lt;<[email protected]>&gt;.
 ### Releases
 
 
-### From outside the list
+### Other news
 
 
 ## Credits