Typo in README.md

In logs_check section,

tests:
- type: logs_check
  ssh:
    host: hostname
    user: username
  ignore_strings:
    - 'string_to_be_ignored_1'
    - 'string_to_be_ignored_2'

ignore_strings may be incorrect key. ignore is correct.

getConfig function corrects ignore strings by using ignore key in logs_check.py https://git.rlab.io/system/healthcheck/blob/master/heruche/tests/logs_check.py#L32