Remove unused Drupal\jsonapi\Normalizer\EntityReferenceFieldNormalizer

I guess this needs a separate patch for 9.5.x when it's committed.

Thanks can we get a 9.5 version too?

Rerolled patch for the 9.5.x branch, please review it.

Thanks & Regards,
Mrinalini

I have reviewed the patch and its working fine.

Needs another re-roll for 10.1.x

Re-roll for 10.1.x
Thanks

Thanks! I hope it's OK for me to RTBC now that neither of the patches are actually from me.

I did a gitlab search just in case someone was using this, and it turns out they are:

https://git.drupalcode.org/project/jsonapi_embed/-/blob/8.x-1.x/src/Norm...

That module doesn't appear to be in use/maintained, but I think we need to follow the 'best effort' deprecation policy, and deprecate this in 10.1.x for removal in 11.0.x and then actually remove it there. Doesn't need test coverage, just the @deprecated and a @trigger_error().