churn: lowercase output

This changes the continuously updated progress bar -- not something a
script would rely on.

hgext/churn.py

@@ -79,7 +79,7 b' def countrate(ui, repo, amap, *pats, **o'
             newpct = int(100.0 * count / max(len(repo), 1))
             if pct < newpct:
                 pct = newpct
-                ui.write(_("\rGenerating stats: %d%%") % pct)
+                ui.write(_("\rgenerating stats: %d%%") % pct)
                 sys.stdout.flush()
 
     if opts.get('progress'):