lavc: postpone removing old audio encoding and decoding API

It has been deprecated only recently.

libavcodec/version.h

@@ -114,13 +114,13 @@
 #define FF_API_DATA_POINTERS (LIBAVCODEC_VERSION_MAJOR < 54)
 #endif
 #ifndef FF_API_OLD_DECODE_AUDIO
-#define FF_API_OLD_DECODE_AUDIO (LIBAVCODEC_VERSION_MAJOR < 54)
+#define FF_API_OLD_DECODE_AUDIO (LIBAVCODEC_VERSION_MAJOR < 55)
 #endif
 #ifndef FF_API_AVFRAME_AGE
 #define FF_API_AVFRAME_AGE (LIBAVCODEC_VERSION_MAJOR < 54)
 #endif
 #ifndef FF_API_OLD_ENCODE_AUDIO
-#define FF_API_OLD_ENCODE_AUDIO (LIBAVCODEC_VERSION_MAJOR < 54)
+#define FF_API_OLD_ENCODE_AUDIO (LIBAVCODEC_VERSION_MAJOR < 55)
 #endif
 
 #endif /* AVCODEC_VERSION_H */