Automation rules: hide custom match field instead of making it read-only when not required

[stsewd]

The field "custom match" is only required when the user selects the custom match option. We used to hide this field in the old dashboard, we are now marking the field as read-only. This can be confusing, as the previous value is still shown, but it's never used.

[stsewd]

I also found that the form isn't respecting the "selected" attribute, it always shows "custom match" as selected.