diff.h: remove unnecessary include of object.h

Signed-off-by: Elijah Newren <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: newren

diff.h

@@ -6,7 +6,6 @@
 
 #include "tree-walk.h"
 #include "pathspec.h"
-#include "object.h"
 #include "oidset.h"
 #include "strbuf.h"