Remove heap_is_swept_object function

is_swept_object just calls heap_is_swept_object so remove
heap_is_swept_object.

gc.c

@@ -4246,23 +4246,12 @@ is_id_value(rb_objspace_t *objspace, VALUE ptr)
 }
 
 static inline int
-heap_is_swept_object(rb_objspace_t *objspace, VALUE ptr)
+is_swept_object(rb_objspace_t *objspace, VALUE ptr)
 {
     struct heap_page *page = GET_HEAP_PAGE(ptr);
     return page->flags.before_sweep ? FALSE : TRUE;
 }
 
-static inline int
-is_swept_object(rb_objspace_t *objspace, VALUE ptr)
-{
-    if (heap_is_swept_object(objspace, ptr)) {
-	return TRUE;
-    }
-    else {
-	return FALSE;
-    }
-}
-
 /* garbage objects will be collected soon. */
 static inline int
 is_garbage_object(rb_objspace_t *objspace, VALUE ptr)