Update signs_description.xml

Fixes first half of rosmord#37:

- Aa18 is a denoted to contain Aa17, but also vice versa. I think it is clear that Aa17 does _not_ include Aa18.
- V98 is a denoted to contain V36, but also vice versa. I think it is clear that V98 does _not_ include V36.
- Y1 is a denoted to contain Y2, but also vice versa. I think it is clear that Y2 does _not_ include Y1.
- D32 is a denoted to contain D197, but also vice versa. I think it is clear that D197 does _not_ include D32.