add test coverage annotation for sdp munging

fixes w3c#2907

Author: fippo

webrtc.html

@@ -4241,7 +4241,7 @@ <h2>
                           </p>
                         </li>
                         <li data-tests=
-                        "RTCPeerConnection-setLocalDescription-offer.html">
+                        "RTCPeerConnection-setLocalDescription-offer.html,legacy/munge-dont.html">
                           <p>
                             If <var>type</var> is {{RTCSdpType/"offer"}}, and
                             <var>sdp</var> is not the empty string and not
@@ -4253,7 +4253,7 @@ <h2>
                           </p>
                         </li>
                         <li data-tests=
-                        "RTCPeerConnection-setLocalDescription-answer.html">
+                        "RTCPeerConnection-setLocalDescription-answer.html,legacy/munge-dont.html">
                           <p>
                             If <var>type</var> is {{RTCSdpType/"answer"}} or
                             {{RTCSdpType/"pranswer"}}, and <var>sdp</var> is