aacdec: remove dead assignment

Signed-off-by: Mans Rullgard <mans@mansr.com>

libavcodec/aacdec.c

@@ -1271,7 +1271,7 @@ static inline float *VMUL4S(float *dst, const float *v, unsigned idx,
     t.i = s.i ^ (sign & 1U<<31);
     *dst++ = v[idx>>4 & 3] * t.f;
 
-    sign <<= nz & 1; nz >>= 1;
+    sign <<= nz & 1;
     t.i = s.i ^ (sign & 1U<<31);
     *dst++ = v[idx>>6 & 3] * t.f;