fix typo

src/foreign/from_cache_esi_deliver.c

@@ -173,7 +173,7 @@ vped_gzgz_init(struct req *req, void **priv)
 
 /*
  * we removed a NULL VDP_FLUSH from _fini because in our code it goes to the
- * _toparent vdp on the same request, rather than one request up as in the
+ * _to_parent vdp on the same request, rather than one request up as in the
  * original code.
  *
  * thus we need to flush at the end of each call