readme: update du status

Author: jgarzik

README.md

@@ -76,6 +76,7 @@ Because it is a FAQ, the major differences between this project and uutils are:
  - [x] delta (SCCS)
  - [x] diff
  - [x] dirname
+ - [x] du
  - [x] echo
  - [x] ex (Editors)
  - [x] expand
@@ -177,7 +178,6 @@ Because it is a FAQ, the major differences between this project and uutils are:
 
  - [x] cal
  - [x] df
- - [x] du
  - [x] dd
  - [x] getconf
  - [x] id