Remove unnecessary directory-modified event

This event was used to re-apply the selected class
to directory entries after their parent directory
was re-rendered. Directory views are not re-rendered
anymore.

Binding a handler to the event was causing a deprecation
warning because the name contains a colon, so it looks
like a command. The easiest fix was to remove it.

Signed-off-by: Nathan Sobo <nathan@github.com>