DiskUsage docs: update screenshots.

- Why were we using old BeOS screenshots here?
- Why is this not part of the user guide anyways?

docs/apps/diskusage/DiskUsage.html

@@ -23,7 +23,9 @@
  
 <p style="text-align:center;"><img src="home.png" alt="DiskUsage home" /></p> 
  
-<p>The circle in the middle represents my <code>/boot/home</code> directory. Each segment of the ring immediately outside that circle represents a file or directory within <code>/boot/home</code>.  And so on.
+<p>The circle in the middle represents my <code>/boot/system</code> directory.
+Each segment of the ring immediately outside that circle represents a file or
+directory within <code>/boot/system</code>.  And so on.
 </p> 
  
 <h3>Usage</h3>