sdp: add missing continue after parsing b= lines

otherwise this shows up in the logs as unhandled when it has been handled.

BUG=None

Change-Id: Ic081312a266d7a7ffff6220d2979cefa29a8591e
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/196652
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32810}

pc/webrtc_sdp.cc

@@ -3059,6 +3059,7 @@ bool ParseContent(const std::string& message,
       }
       media_desc->set_bandwidth(b);
       media_desc->set_bandwidth_type(bandwidth_type);
+      continue;
     }
 
     // Parse the media level connection data.