Remove 400/429 error codes being hidden by default

[jamesmacwhite]

The default configuration example will automatically prevent 400, 404 and 429 error codes being reported by default.

Would it be safer to reduce this to just 404 errors, 400 and 429 might be useful or potentially mask issues. e.g. for 400 errors if there are CSRF issues, these would be masked.

[roelvanhintum]

Thanks @jamesmacwhite, i'll look into this.