test_help_arg: remove assert on 'optional arguments'

[mikelolasagasti]

$ python --version
Python 3.9.2

usage: bandit [-h] [-r] [-a {file,vuln}] [-n CONTEXT_LINES] [-c CONFIG_FILE] [-p PROFILE] [-t TESTS] [-s SKIPS] [-l] [-i] [-f {csv,custom,html,json,screen,txt,xml,yaml}] [--msg-template MSG_TEMPLATE] [-o [OUTPUT_FILE]] [-v] [-d] [-q]
              [--ignore-nosec] [-x EXCLUDED_PATHS] [-b BASELINE] [--ini INI_PATH] [--exit-zero] [--version]
              [targets ...]

Bandit - a Python source code security analyzer

positional arguments:
  targets               source file(s) or directory(s) to be tested

optional arguments:
  -h, --help            show this help message and exit
  -r, --recursive       find and process files in subdirectories
(...)

$ python --version
Python 3.10.0

usage: bandit [-h] [-r] [-a {file,vuln}] [-n CONTEXT_LINES] [-c CONFIG_FILE] [-p PROFILE] [-t TESTS] [-s SKIPS] [-l | --severity-level {all,low,medium,high}] [-i | --confidence-level {all,low,medium,high}]
              [-f {csv,custom,html,json,screen,txt,xml,yaml}] [--msg-template MSG_TEMPLATE] [-o [OUTPUT_FILE]] [-v] [-d] [-q] [--ignore-nosec] [-x EXCLUDED_PATHS] [-b BASELINE] [--ini INI_PATH] [--exit-zero] [--version]
              [targets ...]

Bandit - a Python source code security analyzer

positional arguments:
  targets               source file(s) or directory(s) to be tested

options:
  -h, --help            show this help message and exit
  -r, --recursive       find and process files in subdirectories
(...)