vf_drawtext: Drop wrong void* cast

libavfilter/vf_drawtext.c:844:49: warning: ISO C forbids conversion of function pointer to object pointer type [-Wpedantic]

libavfilter/vf_drawtext.c

@@ -840,7 +840,7 @@ static int draw_glyphs(DrawTextContext *s, AVFrame *frame,
             continue;
 
         dummy.code = code;
-        glyph = av_tree_find(s->glyphs, &dummy, (void *)glyph_cmp, NULL);
+        glyph = av_tree_find(s->glyphs, &dummy, glyph_cmp, NULL);
 
         if (glyph->bitmap.pixel_mode != FT_PIXEL_MODE_MONO &&
             glyph->bitmap.pixel_mode != FT_PIXEL_MODE_GRAY)