LibMedia: Make MatroskaDemuxer::get_codec_id_for_string static

Author: Zaggy1024

Libraries/LibMedia/Containers/Matroska/MatroskaDemuxer.h

@@ -54,7 +54,7 @@ class MatroskaDemuxer final : public Demuxer {
     };
 
     DecoderErrorOr<TrackStatus*> get_track_status(Track track);
-    CodecID get_codec_id_for_string(FlyString const& codec_id);
+    static CodecID get_codec_id_for_string(FlyString const& codec_id);
 
     Reader m_reader;