remove unneeded include

Reference: /n/atom/patch/applied2013/revdumpinc
Date: Tue Jun 18 22:10:16 CES 2013
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/replica/revdump.c	Tue Jun 18 22:10:08 2013
+++ /sys/src/cmd/replica/revdump.c	Tue Jun 18 22:10:08 2013
@@ -1,7 +1,6 @@
 #include <u.h>
 #include <libc.h>
 #include <bio.h>
-#include <disk.h>
 
 static void
 enm(char *new, char *old, Dir *d, void*)