[7.5] Avoid characterizing CSRF_TRUSTED_ORIGINS as a new setting

[jacobtylerwalls]

brief description of changes

CSRF_TRUSTED_ORIGINS isn't new in Arches 7.5 / Django 4.x, it's just more important. We shouldn't discourage people from learning about the setting or debugging it on lower versions.

Inspired by forum post.

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• [x] the PR branch was originally made from the base branch

This box should be checked

• [ ] after these changes the docs build locally without error

This box should only be checked you intend to follow through on it (we can do it on our end too)

• [ ] I will cherry-pick all commits in this PR into other branches that should have them after this PR is merged

[ekansa]

This looks good to me, and is a good clarification. Thanks @jacobtylerwalls !