Revert "#14329 Improve diffs for custom_fields" (#21692)

This reverts commit 38afed60ef.

netbox/core/views.py

@@ -30,7 +30,7 @@ from netbox.views import generic
 from netbox.views.generic.base import BaseObjectView
 from netbox.views.generic.mixins import TableMixin
 from utilities.apps import get_installed_apps
-from utilities.data import deep_compare_dict
+from utilities.data import shallow_compare_dict
 from utilities.forms import ConfirmationForm
 from utilities.htmx import htmx_partial
 from utilities.json import ConfigJSONEncoder
@@ -273,11 +273,14 @@ class ObjectChangeView(generic.ObjectView):
             prechange_data = instance.prechange_data_clean
 
         if prechange_data and instance.postchange_data:
-            diff_added, diff_removed = deep_compare_dict(
+            diff_added = shallow_compare_dict(
                 prechange_data or dict(),
                 instance.postchange_data_clean or dict(),
                 exclude=['last_updated'],
             )
+            diff_removed = {
+                x: prechange_data.get(x) for x in diff_added
+            } if prechange_data else {}
         else:
             diff_added = None
             diff_removed = None