Remove is_a link between 'defense response to other organism' and 'immune response'

[cmungall]

Read all comments on this topic in #16298 before commenting. I think this is the immediate course of action agreed upon (in 2018!) on that ticket.

Immediate course of action:

1. Remove is_a link between 'defense response to other organism' and 'immune response'
2. Examine all descendants of DRtOO and determine if they should be placed under 'immune response' (or ideally a more precise term)
   • E.g. CRISPR-CAS - No

There is a lot more to talk about here, but I suggest limiting this issue to be the immediate action above. We have an issue about CRISPR-CAS #16423 -- the defense response hierarchy seems pretty problematic to me on multiple levels but let's talk about that elsewhere

[pgaudet]

I had added the relation between 'defense response to other organism' and 'immune response' here
#18737 (comment) (but without explanation, probably during a discussion). Now removed.

[pgaudet]

We should discuss this on a multiorg call, also with @addiehl

[addiehl]

See also my long comment to #16423