Avoid to update inlined relation column to NULL when deleting entities When deleting entities, cubicweb run a rql DELETE on all relations to trigger hooks. For an inlined relation this also mean set the column to NULL. This operation may fail if there's additional constraints on the column. Also this is a weird and useless behavior since deleting the entity row will by definition delete the relation. We still doesn't handle the case where both subject and object are going to be deleted because rows need to be deleted in a particular order that cubicweb doesn't handle. Add a test checking UPDATE does not occur but hooks are correctly called. Closes #17236690

### Requirements for tests in various cubicweb/**/test directories. ###

## shared by several test folders
cubicweb-card == 0.5.8
docutils
Twisted < 16.0.0
webtest

## cubicweb/test
Pygments
pycrypto
mock
#fyzz XXX pip install fails
cubicweb-file == 1.18.0
cubicweb-localperms == 0.3.2
cubicweb-tag == 1.8.3

## cubicweb/devtools/test
flake8

## cubicweb/hooks/test
psycopg2-binary

## cubicweb/pyramid/test
pyramid >= 1.5.0
waitress >= 0.8.9
wsgicors >= 0.3
pyramid_multiauth
repoze.lru

## cubicweb/sobject/test
cubicweb-comment == 1.12.2