Remove comments about feature branches

We don't define a concept of a feature branch, so let's not complicate
things.

.github/DEVELOPMENT.md

@@ -29,8 +29,6 @@ there might be preparatory commits at the bottom of the stack that don't bring a
 but none of the commits should introduce an error that is fixed by some future commit.
 Every commit should build and pass all tests.
 
-It is important to keep commits on feature branches neat, squashing the feature branch as necessary.
-
 Commit messages and history are also important, as they are used by other developers to keep track of
 the motivation behind changes. Keep logical diffs grouped together in separate commits, and order commits
 in a way that explains the progress of the changes. Rewriting and reordering commits may be a