Issue #2332 - Update most tests to skip RTCSessionDescription construction

Backport of https://bugzilla.mozilla.org/show_bug.cgi?id=1263312 part 6

dom/media/tests/mochitest/test_peerConnection_restartIceLocalAndRemoteRollback.html

@@ -51,10 +51,8 @@
         },
 
         function PC_REMOTE_ROLLBACK(test) {
-          return test.setRemoteDescription(
-              test.pcRemote,
-              new RTCSessionDescription({ type: "rollback" }),
-              STABLE);
+          return test.setRemoteDescription(test.pcRemote, { type: "rollback" },
+                                           STABLE);
         },
 
         function PC_LOCAL_ROLLBACK(test) {