object.h: Remove obsolete struct object_refs

7914053b (Remove unused object-ref code, 2008-02-25) removed all uses of
the structure from the code, but forgot to remove the type definition
itself.
Signed-off-by: NJakob Pfender <jpfender@elegosoft.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

object.h

@@ -6,11 +6,6 @@ struct object_list {
 	struct object_list *next;
 };
 
-struct object_refs {
-	unsigned count;
-	struct object *ref[FLEX_ARRAY]; /* more */
-};
-
 struct object_array {
 	unsigned int nr;
 	unsigned int alloc;