Delete contradictory text

Now that we don't require that PATH_RESPONSE follow the path of the PATH_CHALLENGE, no sense in requiring here.

Thanks to @erickinnear for noticing this.

draft-ietf-quic-transport.md

@@ -1699,11 +1699,6 @@ it can associate the peer's response with the corresponding PATH_CHALLENGE.
 On receiving a PATH_CHALLENGE frame, an endpoint MUST respond immediately by
 echoing the data contained in the PATH_CHALLENGE frame in a PATH_RESPONSE frame.
 
-To ensure that packets can be both sent to and received from the peer, the
-PATH_RESPONSE MUST be sent on the same path as the triggering PATH_CHALLENGE.
-That is, from the same local address on which the PATH_CHALLENGE was received,
-to the same remote address from which the PATH_CHALLENGE was received.
-
 
 ## Successful Path Validation