fix(gdb): remove duplicate candidates

Author: akinomyoga

completions/gdb

@@ -31,7 +31,7 @@ _comp_cmd_gdb()
                 IFS=$' \t\n'
                 find ${path_array[@]+"${path_array[@]}"} . -name . -o \
                     -type d -prune -o -perm -u+x -print 2>/dev/null |
-                    command sed 's|^.*/||'
+                    command sed 's|^.*/||' | sort -u
             )"
         fi
     elif ((cword == 2)); then