opus: remove redundant ff_celt_window2 declaration

Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>

libavcodec/opus.h

@@ -205,6 +205,4 @@ int ff_celt_decode_frame(CeltContext *s, OpusRangeCoder *rc,
                          float **output, int coded_channels, int frame_size,
                          int startband,  int endband);
 
-extern const float ff_celt_window2[120];
-
 #endif /* AVCODEC_OPUS_H */

libavcodec/opusdec.c

@@ -47,6 +47,7 @@
 #include "internal.h"
 #include "mathops.h"
 #include "opus.h"
+#include "opustab.h"
 
 static const uint16_t silk_frame_duration_ms[16] = {
     10, 20, 40, 60,