Bug 1546981: Remove duplicate test-case, and remove an error suppression it caused. r=jib

Differential Revision: https://phabricator.services.mozilla.com/D29667

--HG--
extra : moz-landing-system : lando

testing/web-platform/meta/webrtc/RTCPeerConnection-setLocalDescription-answer.html.ini

@@ -1,2 +0,0 @@
-[RTCPeerConnection-setLocalDescription-answer.html]
-  expected: ERROR

testing/web-platform/tests/webrtc/RTCPeerConnection-setLocalDescription-answer.html

@@ -186,19 +186,4 @@
     await pc2.setLocalDescription(answer); // Should check against [[LastAnswer]], not [[LastOffer]]
   }, "Setting previously generated answer after a call to createOffer should work");
 
-  promise_test(async t => {
-    const pc1 = new RTCPeerConnection();
-    t.add_cleanup(() => pc1.close());
-    const pc2 = new RTCPeerConnection();
-    t.add_cleanup(() => pc2.close());
-
-    const offer = await pc1.createOffer({offerToReceiveAudio: true});
-    await pc2.setRemoteDescription(offer);
-    const answer = await pc2.createAnswer(); // [[LastAnswer]] slot set
-    await pc2.setRemoteDescription({type: "rollback"});
-    await pc2.createOffer({offerToReceiveVideo: true}); // [[LastOffer]] slot set
-    await pc2.setRemoteDescription(offer);
-    await pc2.setLocalDescription(answer); // Should check against [[LastAnswer]], not [[LastOffer]]
-  }, "Setting previously generated answer after a call to createOffer should work");
-
 </script>