Reland "Delete VideoCodec::plName"

This is a reland of 89d88c0b9d61975bc63623ab8028377d8f9733dc

Original change's description:
> Delete VideoCodec::plName
> 
> All use was deleted in cl https://webrtc-review.googlesource.com/56100, now
> delete the actual member too.
> 
> Bug: webrtc:8830
> Change-Id: Iabbfd8eb08078e39a8e57f33f7c6a9de4bc3b6cb
> Reviewed-on: https://webrtc-review.googlesource.com/60300
> Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
> Commit-Queue: Niels Moller <nisse@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#22353}

Bug: webrtc:8830
Change-Id: I902c1ee5bfb1bc8b842702d433798d338261587b
Reviewed-on: https://webrtc-review.googlesource.com/60902
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22396}
diff --git a/common_types.h b/common_types.h
index 682a202..ee4ddf7 100644
--- a/common_types.h
+++ b/common_types.h
@@ -397,8 +397,6 @@
 };
 
 // Video codec
-// TODO(nisse): Delete together with VideoCodec::plName, below.
-enum { kPayloadNameSize = 32 };
 enum { kMaxSimulcastStreams = 4 };
 enum { kMaxSpatialLayers = 5 };
 enum { kMaxTemporalStreams = 4 };
@@ -521,9 +519,6 @@
 
   // Public variables. TODO(hta): Make them private with accessors.
   VideoCodecType codecType;
-  // TODO(nisse): Unused in webrtc, delete as soon as downstream
-  // applications are updated to not use it.
-  char plName[kPayloadNameSize];
   unsigned char plType;
 
   unsigned short width;