fftools/ffmpeg_opt: Add a missing closing brackets.

Fixes ticket #8447.

fftools/ffmpeg_opt.c

@@ -3202,7 +3202,7 @@ void show_help_default(const char *opt, const char *arg)
                       OPT_EXIT, 0, 0);
 
     show_help_options(options, "Global options (affect whole program "
-                      "instead of just one file:",
+                      "instead of just one file):",
                       0, per_file | OPT_EXIT | OPT_EXPERT, 0);
     if (show_advanced)
         show_help_options(options, "Advanced global options:", OPT_EXPERT,