avfilter/vf_fftfilt: Remove dead depth code

Fixes: CID1509373 Logically dead code

Sponsored-by: Sovereign Tech Fund
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavfilter/vf_fftfilt.c

@@ -382,11 +382,9 @@ static int config_props(AVFilterLink *inlink)
     if (s->depth <= 8) {
         s->rdft_horizontal = rdft_horizontal8;
         s->irdft_horizontal = irdft_horizontal8;
-    } else if (s->depth > 8) {
+    } else {
         s->rdft_horizontal = rdft_horizontal16;
         s->irdft_horizontal = irdft_horizontal16;
-    } else {
-        return AVERROR_BUG;
     }
     return 0;
 }