libavformat: Remove a misleading/incorrect comment

This comment can be traced back to the initial commit from 2001,
and it seemed to be misleading/incorect already back then. (It
was used for normal, non-raw file formats already then.)
Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/avformat.h

@@ -577,8 +577,8 @@ typedef struct AVInputFormat {
 
     /**
      * Read the format header and initialize the AVFormatContext
-     * structure. Return 0 if OK. Only used in raw format right
-     * now. 'avformat_new_stream' should be called to create new streams.
+     * structure. Return 0 if OK. 'avformat_new_stream' should be
+     * called to create new streams.
      */
     int (*read_header)(struct AVFormatContext *);