Fix class/struct mismatching

- fixes class/struct mismatches in forward declarations

Change-Id: I4118d63fd24b817ef6bbb6cd5d6d551dfaa6c78b

src/media/media_encoder.h

@@ -47,8 +47,8 @@ namespace ring {
 
 class AudioBuffer;
 class MediaIOHandle;
-class MediaDescription;
-class AccountCodecInfo;
+struct MediaDescription;
+struct AccountCodecInfo;
 
 class MediaEncoderException : public std::runtime_error {
     public:

src/media/video/video_sender.h

@@ -34,7 +34,7 @@
 // Forward declarations
 namespace ring {
 class SocketPair;
-class AccountVideoCodecInfo;
+struct AccountVideoCodecInfo;
 }
 
 namespace ring { namespace video {