avfilter: remove obsolete FF_API_BUFFERSRC_BUFFER cruft

Reviewed-by: Michael Niedermayer <michaelni@gmx.at>
Signed-off-by: James Almer <jamrial@gmail.com>

libavfilter/version.h

@@ -58,9 +58,6 @@
 #ifndef FF_API_FILL_FRAME
 #define FF_API_FILL_FRAME                   (LIBAVFILTER_VERSION_MAJOR < 5)
 #endif
-#ifndef FF_API_BUFFERSRC_BUFFER
-#define FF_API_BUFFERSRC_BUFFER             (LIBAVFILTER_VERSION_MAJOR < 5)
-#endif
 #ifndef FF_API_AVFILTERBUFFER
 #define FF_API_AVFILTERBUFFER               (LIBAVFILTER_VERSION_MAJOR < 6)
 #endif