qemu-img: Fix copy+paste bug in documentation

Replace rebase by resize in documentation of resize command.

Cc: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Cc: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: NStefan Weil <weil@mail.berlios.de>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

qemu-img-cmds.hx

@@ -54,6 +54,6 @@ ETEXI
 DEF("resize", img_resize,
     "resize filename [+ | -]size")
 STEXI
-@item rebase @var{filename} [+ | -]@var{size}
+@item resize @var{filename} [+ | -]@var{size}
 @end table
 ETEXI