Remove default value at fail_on_error

[mongolyy]

-fail-on-error is deprecated.
https://github.com/reviewdog/reviewdog/blob/master/CHANGELOG.md#rotating_light-deprecation-warnings

However, this workflow depends on reviewdog/action-suggester, which does not support -fail-level.

Until the action-suggester is improved, I focus on backward compatibility and set the default value to -fail-on-error at #80.

Once the action-suggester is improved, we will delete the default value.
Related to: reviewdog/action-suggester#64

[mongolyy]

I think it's better not to delete the default value(false) of fail_on_error.

For two reasons

• If fail_on_error is false, the value of fail_level is used, so it does not affect the fail_level setting
  • https://github.com/reviewdog/reviewdog/blob/v0.20.3/cmd/reviewdog/main.go#L1045-L1058
• Other workflows maintained by the reviewdog organization have default value.
  • https://github.com/reviewdog/action-rubocop/blob/v2.21.0/action.yml#L12-L18
  • https://github.com/reviewdog/action-eslint/blob/v1.33.0/action.yml#L32-L39

So, I modify some comments using other workflows as a reference.