fix game_name or gn->n typo

[lasers]

Hi. If I want to sort by game_name, the manual page say I can use game_name or n.

  -s SORT, --sort SORT  sort search output by column name, can string multiple names by using a comma.  Available options are: console or c, title_id or id, region or r,
                        type or t, game_name or n, size or s. Default value: c,t,r,n

Using game_name works fine.

Using n gives this error.

[ERROR] invalid list for --order

Using gn gives this error.

Traceback (most recent call last):
  File "~/src/pynps/.venv/bin/pynps", line 33, in <module>
    sys.exit(load_entry_point('pynps', 'console_scripts', 'pynps')())
  File "~/src/pynps/pynps/cli/cli.py", line 291, in cli_main
    maybe_download = search_db(system, what_to_dl, args.search, reg, args.sort, DBFOLDER)
  File "~/~src/pynps/pynps/functions/functions.py", line 579, in search_db
    order = [variables.ORDER_DIC[x] for x in order.split(",")]
  File "~/src/pynps/pynps/functions/functions.py", line 579, in <listcomp>
    order = [variables.ORDER_DIC[x] for x in order.split(",")]
KeyError: 'gn'

Simple gn->n typo fix. Thank you for this tool. I hope you don't stop working on it. :-)