Update development.md
update to new main branch naming convention.
@@ -46,7 +46,7 @@ make
*Typically for contributing you'll want to
[create a fork](https://help.github.com/en/articles/fork-a-repo) and use that
-but for purpose of this guide we'll be using the upstream/master.*
+but for purpose of this guide we'll be using the upstream/main.*
## Building code and images
