vp8dsp: Remove the comment saying that the height is equal to the width

This comment isn't true, the height can be different from the width
for these functions (which is why the height is passed as a parameter
to them).
Signed-off-by: Martin Storsjö <martin@martin.st>

libavcodec/vp8dsp.h

@@ -70,7 +70,7 @@ typedef struct VP8DSPContext {
     void (*vp8_h_loop_filter_simple)(uint8_t *dst, ptrdiff_t stride, int flim);
 
     /**
-     * first dimension: 4-log2(width), height is assumed equal to width
+     * first dimension: 4-log2(width)
      * second dimension: 0 if no vertical interpolation is needed;
      *                   1 4-tap vertical interpolation filter (my & 1)
      *                   2 6-tap vertical interpolation filter (!(my & 1))