ui-stats: Remove unnecessary #include

<string-list.h> is already #included from cgit.h

Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Lars Hjemli <hjemli@gmail.com>

ui-stats.c

@@ -1,5 +1,3 @@
-#include <string-list.h>
-
 #include "cgit.h"
 #include "html.h"
 #include "ui-shared.h"