avfilter/vf_showpalette: fix small cosmetics issue

libavfilter/vf_showpalette.c

@@ -96,7 +96,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
     int ret;
     AVFrame *out;
     AVFilterContext *ctx = inlink->dst;
-    const ShowPaletteContext *s= ctx->priv;
+    const ShowPaletteContext *s = ctx->priv;
     AVFilterLink *outlink = ctx->outputs[0];
 
     out = ff_get_video_buffer(outlink, outlink->w, outlink->h);