Remove ? in [[?FOO]] as it is not (any longer?) valid bikeshed syntax.

Author: jan-ivar

index.bs

@@ -371,7 +371,7 @@ dictionary RTCEncodedVideoFrameMetadata {
     <dd>
         <p>
             An identifier for the encoded frame, monotonically increasing in decode order. Its lower
-            16 bits match the frame_number of the AV1 Dependency Descriptor Header Extension defined in Appendix A of [[?AV1-RTP-SPEC]], if present.
+            16 bits match the frame_number of the AV1 Dependency Descriptor Header Extension defined in Appendix A of [[AV1-RTP-SPEC]], if present.
             Only present for received frames if the Dependency Descriptor Header Extension is present.
         </p>
     </dd>
@@ -381,7 +381,7 @@ dictionary RTCEncodedVideoFrameMetadata {
     <dd>
         <p>
             List of frameIds of frames this frame references.
-            Only present for received frames if the AV1 Dependency Descriptor Header Extension defined in Appendix A of [[?AV1-RTP-SPEC]] is present.
+            Only present for received frames if the AV1 Dependency Descriptor Header Extension defined in Appendix A of [[AV1-RTP-SPEC]] is present.
         </p>
     </dd>
     <dt>