Fixes #6874: Integers in settings can be up to 8 digits to avoid bigint out of range error

@domcleal I couldn't use `refute_valid setting, :value, "is too long (maximum is 8 characters)"` as you suggested, the test failed with `value error matching is too long (maximum is 8 characters) not found: ["is too long (maximum is 8 characters)"]` 
I changed the test above mine that was also using the old syntax and it works fine so I think it has something to do with the parenthesis in the error message