lavf: undeprecate read_seek().

The "new seeking API" was never finished and nobody is working on it.

libavformat/avformat.h

@@ -503,7 +503,6 @@ typedef struct AVInputFormat {
      */
     int (*read_close)(struct AVFormatContext *);
 
-#if FF_API_READ_SEEK
     /**
      * Seek to a given timestamp relative to the frames in
      * stream component stream_index.
@@ -512,9 +511,9 @@ typedef struct AVInputFormat {
      *              match is available.
      * @return >= 0 on success (but not necessarily the new offset)
      */
-    attribute_deprecated int (*read_seek)(struct AVFormatContext *,
-                                          int stream_index, int64_t timestamp, int flags);
-#endif
+    int (*read_seek)(struct AVFormatContext *,
+                     int stream_index, int64_t timestamp, int flags);
+
     /**
      * Get the next timestamp in stream[stream_index].time_base units.
      * @return the timestamp or AV_NOPTS_VALUE if an error occurred

libavformat/version.h

@@ -50,9 +50,6 @@
 #ifndef FF_API_OLD_METADATA2
 #define FF_API_OLD_METADATA2           (LIBAVFORMAT_VERSION_MAJOR < 54)
 #endif
-#ifndef FF_API_READ_SEEK
-#define FF_API_READ_SEEK               (LIBAVFORMAT_VERSION_MAJOR < 54)
-#endif
 #ifndef FF_API_OLD_AVIO
 #define FF_API_OLD_AVIO                (LIBAVFORMAT_VERSION_MAJOR < 54)
 #endif